Maintaining quality in file based video

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  • Tektronix July 15, 2010 Vision 07
  • Tektronix July 15, 2010 Vision 07
  • Tektronix July 15, 2010 Vision 07 It’s a cliché now but we all know the numerous devices and formats that video is or will be appearing on: The key things here are: there are a new set of competing broadcasters there are new and vastly different technical requirements Digital video roll-out and technology transition HD seen a broadcast differentiator, becoming the “ante” Consumer electronics driving innovation and adoption Shift from managing signals to managing content Increasing use of file based formats for storage and editing Helping the customer quickly interpret digital results is important Content anywhere, anytime Telco’s investing to deliver video through networks Next generation compression and IP technologies enabling IPTV, mobile video and video over IP Increase in re-purposing for multiple display platforms Broadcasters challenged to profitably transition to digital Fewer resources and de-skilling Shift from video to IT skill set
  • Tektronix July 15, 2010 Vision 07 Digital broadcasting allows more channels to air, Viewers have more choice, channels need to gain and retain viewer loyalty Maintain good business model by retaining and attracting advertisers through competitive rates and growing viewer ratings attaining and maintaining lowest operational costs Possibility to increase penetration by utilising increasing number of delivery mechanisms
  • Tektronix July 15, 2010 Vision 07 In recent times the broadcasting workflow has changed. We have moved from analog to digital production, analog tape to digital tape, signals sent around facilities and between facilities as a digital signal. The amount of digital video data far exceeding any economic IT storage solution. Thanks to advances in compression technology and storage prices, video traditionally stored on tape can now be economically stored on disk. The entire broadcasting workflow is getting more complex with distribution via; not just Standard Definition but also High Definition and many other resolutions to suit the new distribution media. There has been an exponential growth of the Video Server market globally. More and more broadcasters are turning to ingest, manage, store and playout their video assets from Video Servers. Reports from companies such as Frost & Sullivan estimate that revenues from video servers will be around $900 million per annum by 2010 - more than 2.5 times the figure in 2006. Ingest, automation and playout systems are being upgraded to deal with all the new media types. At ingest, though, how does a broadcaster know that the video file they have just received meets their requirements?
  • Tektronix July 15, 2010 Vision 07 We will now talk through a general file based workflow for a broadcaster starting at ingest and finishing at playout
  • Tektronix July 15, 2010 Vision 07 An MPEG 2 50Mb/s I frame only master can be transcoded to Windows media, ipod movie for download
  • Tektronix July 15, 2010 Vision 07 Here I will talk about the different codecs we come across in video compression.
  • Tektronix July 15, 2010 Vision 07 The three most common compression systems used by broadcasters are: MPEG 2 VC-1 H.264 Each have different benefits of compression, interoperability and complexity of decoder requirements
  • Tektronix July 15, 2010 Vision 07 The three most common compression systems used by broadcasters are: MPEG 2 VC-1 H.264 Each have different benefits of compression, interoperability and complexity of decoder requirements
  • Tektronix July 15, 2010 Vision 07 Systems layer carrying video, audio and meta data payloads Used extensively for digital broadcast (DVB & ATSC) Can carry multiple video payloads with multiple associated audio payloads (multi-language / multi-format) Other data such as EPG (Electronic Programme Guide) carried with multiplex Each payload is carried on a distinct PID (Programme ID) Some uses require certain payloads on specific PIDs Transport Streams with only one video payload are called SPTS (Single Program Transport Streams) SPTS common format for ingest operations Transport Streams can carry Program Streams and other Transport streams Statistical multiplexing used for playout operations Simplified version of Transport Streams Only carries one video payload Can carry multiple audio payloads for video Used by Cable for VOD Used by archives and video servers Can carry ancillary data in “private streams” (e.g. meta data, proprietary audio formats)
  • Tektronix July 15, 2010 Vision 07 Profiles dictate the level of coding, which features of the specification are used (therefore the level of complexity required by the decoder) E.g. Main Profile – regular television encoding
  • Tektronix July 15, 2010 Vision 07 Levels specify minimum and maximum parameters of the video, for example: Main Level – standard definition television High Level – high definition television
  • Tektronix July 15, 2010 Vision 07
  • Tektronix July 15, 2010 Vision 07 Add picture of X-Box
  • Tektronix July 15, 2010 Vision 07 VC-1 contains a number of profile and level combinations that support the encoding of many types of video The profile determines the codec features that are available, and therefore determines the required decoder complexity (mathematical intensity)
  • Tektronix July 15, 2010 Vision 07 From the MPEG side the standard is called MPEG-4 Part 10 (ISO 14496-10) From the ITU side, it is called H.264 (the ITU document number), by which the format is widely known already The "official" title for the new standard Advanced Video Coding (AVC) was chosen by MPEG - as video counterpart to the Advanced Audio Coding (AAC) audio format
  • Tektronix July 15, 2010 Vision 07 From the MPEG side the standard is called MPEG-4 Part 10 (ISO 14496-10) From the ITU side, it is called H.264 (the ITU document number), by which the format is widely known already The "official" title for the new standard Advanced Video Coding (AVC) was chosen by MPEG - as video counterpart to the Advanced Audio Coding (AAC) audio format
  • Tektronix July 15, 2010 Vision 07 USES: Recognised by many as THE upcoming video format, which will be widely used and supported, like it is the case with MPEG-2 today MPEG-4 AVC/H.264 is a mandatory standard for HD-DVD and Blu-ray formats The Digital Video Broadcast (DVB) standards body in Europe have approved the use of H.264/AVC for broadcast television in Europe The codec of choice for new HD TV platforms Used in VOD applications The 3rd Generation Partnership Project (3GPP) has approved the inclusion of H.264/AVC as an optional feature in release 6 of its mobile multimedia telephony services specifications
  • Tektronix July 15, 2010 Vision 07
  • Tektronix July 15, 2010 Vision 07 DMS-1 metadata plugin Scalability Single frame to full length motion picture Hundreds of audio channels Metadata rich Real time streamable files No HANC or VBI constraints Interrupted transfers Switched transfers Join mid stream Simultaneous read while write Non real time file transfer Fast random access to material Partial file transfers Synchronize multiple essence types Audio, Video, Metadata
  • Tektronix July 15, 2010 Vision 07 Typical errors in video files can be in any of three layers. Visible artifacts – content layer errors Picture quality looks good but the signal is illegal – gamut error on a waveform monitor The stream stops halfway through – the stream is broken or erroneous Encoder setting errors regarding format, picture resolution Header and wrapper errors These layers are more abstract from the original analogue electrical signal Will my file play back on a set-top box?
  • Tektronix July 15, 2010 Vision 07 We can look at the test requirements in stack form, from baseband testing at the bottom, to quality at the top – almost like an ISO stack, with increasing abstraction from the physical video signal data as we go further up the stack Syntax of stream priority over baseband tests
  • Tektronix July 15, 2010 Vision 07 Lets look at the creation of a Transport stream for a VoD application. Starting at the bottom of the video abstraction stack, looking at the baseband analogue tests. [Standard solutions] ..these give the standard sorts of displays such as - waveform displays; vector displays diamond (RGB gamut) displays; “ arrow-head” displays – composite violation; with alarm logs
  • Tektronix July 15, 2010 Vision 07 Certainly, SDI monitoring systems are getting more intelligent, providing not only all the ‘analogue’ type displays, but also showing errors in the digital signals. The SDI signal itself can be the source of errors – in a sense, nothing is digital in that if the ‘digital’ levels are incorrect or there is signal ringing, the bits can be misinterpreted. This is an example of SDI signal test on a waveform monitor: the fuzziness of the lines shows the amount of signal jitter. For more information on all these types of test equipment, please go to the Tektronix booth.
  • Tektronix July 15, 2010 Vision 07 Encapsulated within the packetization and CRC data of an MPEG-2 Transport Stream there are four functional components: video, audio, meta-data and TS tables, time-multiplexed. Some of the errors that can be generated in MPEG-2 TS ASI streams (in addition to the analog errors and SD errors) include: CLICK * MPEG-2 video encoding errors - syntax errors introduced in the encoder or during the multiplexing/de-multiplexing processes CLICK * likewise, audio syntax errors CLICK * errors in associated meta data CLICK * errors in PIDs, PATs, PMTs (e.g. scrambling of the data tables for these, or where they appear too infrequently) CLICK The video and audio data can be hundreds of Megabytes or more, and they are interleaved throughout the packets. Normally, the meta-data appears at the start of the Transport Stream, and is repeated at intervals in many transport streams, to allow seamless re-synchronisation/re-start in the event of data corruption or signal loss.
  • Tektronix July 15, 2010 Vision 07 The video and audio in their respective Elementary Streams has usually been compressed, to reduce the bandwidth required to send. The compression schemes are complex, particularly for video, and can themselves generate many errors, particularly with the new H.264/AVC or MPEG-4 Part 10 video compression standard, which is perhaps 4-6 times more complex than MPEG-2 compression. It is also very important to understand that although you could have a perfectly legal TS – the ES could be illegal and the video or audio won’t play, for example, as suggested here, the Video had bit errors during the encoding, but the Transport Stream mux is not aware of this and the video data has been taken and packetized anyway.
  • Tektronix July 15, 2010 Vision 07 This is a frame from what was a legal TS but there was an Elementary Stream error in the video – I assume you all saw the error? Let me run it again. TIME 06:04 FOR ERROR NOW CLICK MOUSE <Read bullets> There were customer complaints – but as the broadcaster had done a ‘full’ QC the broadcaster naturally assumed it was customer’s finger trouble
  • Tektronix July 15, 2010 Vision 07 A video stream can be perfectly legal and syntactically correct but still be unusable by the broadcaster. For example: the broadcaster wants 720x608 resolution to include some of the vertical interval but the video has been supplied/encoded at 720x576 English audio is required to be on channels 1 & 2 (Spanish on 3 & 4) but these have been swapped the peak bit-rate should be 4.5 MBits/sec, but actually goes to 4.6MBit/sec ingested video is expected to have color bars for the first 3 seconds and 400Hz tone for the first 2 seconds, but the times for each have been inadvertently swapped Typically there are many such parameters that need to be right for a broadcaster, and many of these are hard or time-consuming to check on every video file using conventional equipment .
  • Tektronix July 15, 2010 Vision 07
  • Tektronix July 15, 2010 Vision 07
  • Tektronix July 15, 2010 Vision 07
  • Tektronix July 15, 2010 Vision 07
  • Tektronix July 15, 2010 Vision 07
  • Tektronix July 15, 2010 Vision 07
  • Tektronix July 15, 2010 Vision 07
  • Tektronix July 15, 2010 Vision 07
  • Tektronix July 15, 2010 Vision 07 Decoding the encoded file back to baseband for QC may mask errors in the bitstream that may cause a set top box (STB) to produce a black frame, freeze or even worse crash. A professional decoder may mask these errors. So, we should move up the stack to monitor the stream in its native file format rather than decoding. Different file wrapper formats (such as MXF, ASF ™, QuickTime ™, Windows Media ®, 3GPP) and different transport mechanisms (such as IP/RTP), which are used to transmit these different formats, require different analysis and monitoring software. From a complexity viewpoint, each of these will have their own specific sets of common problems to be monitored and diagnosed. Up one more level to look at the Elementary Streams which are encapsulated within the MPEG-2 Transport Stream. There are three functional components: video, audio and meta-data, time-multiplexed each in their own logical data stream. There can also be multiple sets of video, audio and meta-data. Errors typically occur separately in the Elementary Streams as well as in the meta-data - that is, there could be a perfectly legal and correct Transport Stream, but the video or audio Elementary Stream or meta-data is incorrect. The process of compressing the video and audio signals is complex and can itself generate many errors. The newer video compression schemes - H.264/AVC (a.k.a. MPEG-4 Part 10) and VC-1 are more complex than MEPG-2 and give much greater scope for errors.
  • Maintaining quality in file based video

    1. 1. Tom Perry – Tektronix Bristol Maintaining Quality in File Based Video
    2. 2. Outline <ul><li>What is file-based video? </li></ul><ul><li>Video compression </li></ul><ul><li>Challenges of file-based video quality control </li></ul><ul><li>Automatic quality control for file-based video </li></ul>Vision08, 03.2008 Maintaining Quality in File Based
    3. 3. What is File-Based Video ?
    4. 4. Brave new digital world <ul><li>New broadcasters </li></ul><ul><ul><li>not just TV, satellite, cable, but also </li></ul></ul><ul><ul><li>wireless </li></ul></ul><ul><ul><li>VOD </li></ul></ul><ul><ul><li>internet </li></ul></ul><ul><ul><li>podcasters </li></ul></ul><ul><li>New, very different technical requirements </li></ul><ul><ul><li>new codecs </li></ul></ul><ul><ul><li>new formats, resolutions, frame rates, quality levels </li></ul></ul><ul><ul><li>re-purposing and re-encoding </li></ul></ul>Vision08, 03.2008 Maintaining Quality in File Based
    5. 5. Broadcaster Technology Challenges <ul><li>Content file integrity </li></ul><ul><ul><li>Correctly encoded on ingest </li></ul></ul><ul><ul><li>Ensure files are not corrupted during movement, copying and transcoding processes </li></ul></ul><ul><li>Support multiple delivery platforms and formats </li></ul><ul><ul><li>Terrestrial DTV, Satellite, Cable </li></ul></ul><ul><ul><li>Mobile video </li></ul></ul><ul><ul><li>Streaming </li></ul></ul><ul><ul><li>MPEG-2 </li></ul></ul><ul><ul><li>HD </li></ul></ul><ul><ul><li>Podcasts, internet (H.264, MPEG-4, VC-1), VoD (H.264) </li></ul></ul><ul><ul><li>More… </li></ul></ul>Vision08, 03.2008 Maintaining Quality in File Based
    6. 6. Changes in Workflow <ul><li>Increase in compression and decrease in hard disk prices </li></ul><ul><li>Exponential growth of the Video Server market globally </li></ul><ul><li>Broadcasters are turning to ingest, manage, store and playout their video assets from Video Servers </li></ul><ul><li>Complex distribution via terrestrial, satellite, cable, internet and mobile </li></ul><ul><li>Content is being re-purposed at different resolutions and frame rates, using new codecs and at different bit-rates, with different technical requirements </li></ul>Vision08, 03.2008 Maintaining Quality in File Based
    7. 7. Broadcast technical challenges Vision08, 03.2008 <ul><li>Broadcasting Key Challenges </li></ul><ul><li>Reliably store, aggregate and distribute more content in more formats for new distribution paths </li></ul><ul><li>Mastering New Technologies: </li></ul><ul><li>File based Workflow </li></ul><ul><li>HD, H.264, MPEG4, VC1, VOD, Video over IP </li></ul><ul><li>Challenges </li></ul><ul><li>Explosion of content and formats </li></ul><ul><li>Need to QC ingested content from multiple sources </li></ul><ul><li>Human QC not sufficient and not 24/7 </li></ul>Content Delivery Ingest Servers Edit, Schedule & Monitor Playout Servers Terrestrial VOD IPTV Archive News Feeds Sport Movies Post production File based workflow Satellite Maintaining Quality in File Based Ingest Edit Schedule Playout
    8. 8. Typical Workflow Vision08, 03.2008 Maintaining Quality in File Based
    9. 9. Ingest <ul><li>Management software controls tape or line ingest </li></ul><ul><li>Serial Digital Video signal is encoded to a compressed format </li></ul><ul><li>SDI is monitored on waveform monitor for gamut errors and audio peaks. </li></ul><ul><li>Compressed video is wrapped with audio tracks, timecode information and metadata </li></ul><ul><li>Encoded and wrapped file is played back to check quality. Measurements made on waveform monitor. </li></ul>Vision08, 03.2008 Maintaining Quality in File Based
    10. 10. Storage <ul><li>Encoded files are stored in nearline storage </li></ul><ul><li>High resolution master files can be transcoded and repurposed for delivery to different customers </li></ul>Vision08, 03.2008 Maintaining Quality in File Based
    11. 11. Archive <ul><li>Material is moved to the archive after playout or if ingest is advanced a long time of playout </li></ul><ul><li>Material is restored from the archive </li></ul><ul><li>Content metadata can be searched and relevant clips restored </li></ul>Vision08, 03.2008 Maintaining Quality in File Based
    12. 12. Playout <ul><li>Today there can be many outputs from a broadcaster </li></ul><ul><ul><li>Streaming Web site </li></ul></ul><ul><ul><li>IPTV Delivery </li></ul></ul><ul><ul><li>HD/SD Traditional Broadcast </li></ul></ul><ul><ul><li>3G Mobile delivery </li></ul></ul><ul><li>All these components require file based QC </li></ul>Vision08, 03.2008 Maintaining Quality in File Based
    13. 13. File-Based Video Compression
    14. 14. Typical Applications of different codecs Vision08, 03.2008 Maintaining Quality in File Based Video Codec Typical applications (new) MPEG-2 Broadcast, cable, VOD, DVD H.264 / AVC / MPEG-4 Pt 10 Broadcast, cable, VOD, HD, Internet, HD video disks* WM9/VC-1 Broadcast, HD, Internet TV, HD video discs – Blu-Ray DV/DVC-Pro 25/50 Broadcast, Acquisition, Editing MPEG-4 Pt 2 Mobile
    15. 15. Typical Applications of different codecs Vision08, 03.2008 Maintaining Quality in File Based Video Codec Typical applications (new) DNxHD/VC-3 Editing, Broadcast Playout AVC-Intra Acquisition, Editing Pro-Res Editing, iTunes JPEG 2000 D-Cinema, broadcast internal use/archive DVC-Pro100 Acquisition, Editing, Broadcast Playout
    16. 16. MPEG-2: History & Use <ul><li>MPEG-2 is for the generic coding of moving pictures and associated audio </li></ul><ul><li>MPEG-2 (1994) is the designation for a group of coding standards for digital audio and video </li></ul><ul><li>Agreed upon by MPEG (Moving Pictures Experts Group), and published as the ISO/IEC 13818 international standard </li></ul><ul><li>Typically used to encode audio and video for broadcast signals </li></ul><ul><ul><li>Direct broadcast satellite & terrestrial digital TV </li></ul></ul><ul><ul><li>Cable TV </li></ul></ul><ul><ul><li>Video on demand (cable & IP) </li></ul></ul><ul><ul><li>DVD </li></ul></ul>Vision08, 03.2008 Maintaining Quality in File Based
    17. 17. MPEG-2: Profiles Vision08, 03.2008 Maintaining Quality in File Based Abbr. Name Frame Types Colour Format SP Simple Profile I, P 4:2:0 MP Main Profile I, P, B 4:2:0 422P 4:2:2 Profile I, P, B 4:2:2 SNR Single to Noise Ratio I, P, B 4:2:0 SP Spatial Profile I, P, B 4:2:0 HP High Profile I, P, B 4:2:2
    18. 18. MPEG-2: Levels Vision08, 03.2008 Maintaining Quality in File Based Abbr. Name Frame Rate (Max) Pixel/Line (Max) Lines (Max) LL Low Level 30 352 288 ML Main Level 30 720 576 H-14 High 1440 30 1440 1152 HL High Level 30 1920 1152
    19. 19. MPEG-2: Typical Configurations <ul><li>SDTV, DVD </li></ul><ul><ul><li>MP@ML, 720 × 480 or 720 × 576, 4:2:0 colour format, 29.97 or 25 fps </li></ul></ul><ul><li>HDTV </li></ul><ul><ul><li>MP@HL, 1920 × 1080i or 1280 × 720p, 4:2:0 colour format, 30 or 60 fps </li></ul></ul><ul><li>Ingest (Sony IMX I-Frame Only ) </li></ul><ul><ul><li>422P@ML, 720 × 480, 4:2:2 colour format, 30 or 60 fps </li></ul></ul>Vision08, 03.2008 Maintaining Quality in File Based
    20. 20. VC-1: Use <ul><li>Implemented by Microsoft as Windows Media Video (WMV) 9 Advanced Profile, allowing WM content to be delivered over traditional broadcast and wireless infrastructures </li></ul><ul><li>Mandated codec for next-generation DVD (Blu-ray) – all devices will be capable of decoding VC-1 </li></ul><ul><li>Used in Taiwan on their proprietary DVD format – “forward versatile disc” (FVD) </li></ul><ul><li>Microsoft has designated VC-1 as the Xbox 360 video game console's official video codec </li></ul><ul><li>Now a SMPTE standard </li></ul>Vision08, 03.2008 Maintaining Quality in File Based
    21. 21. VC-1: Selected Profile & Level Combo’s Vision08, 03.2008 Maintaining Quality in File Based Profile Level Max Bitrate Example Use Main Medium 10 Mbps 720 x 480 @ 30 Hz (480p) 720 x 576 @ 25 Hz (576p) Main High 20 Mbps 1920 x 1080 @ 30 Hz (1080p) Advanced L1 10 Mbps 720 x 480 @ 30 Hz (NTSC-SD) 720 x 576 @ 25 Hz (PAL-SD) Advanced L3 45 Mbps 1920 x 1080 @ 24 Hz (1080p) 1920 x 1080 @ 30 Hz (1080i) 1280 x 720 @ 60 Hz (720p) Advanced L4 135 Mbps 1920 x 1080 @ 60 Hz (1080p) 2048 x 1536 @ 24 Hz
    22. 22. AVC: MPEG-4 Standards <ul><li>The MPEG-4 Standard is divided into many different sub-standards, below are some selected parts: </li></ul><ul><ul><li>ISO 14496-1 (Systems), Animation/Interactivity (like DVD Menus) </li></ul></ul><ul><ul><li>ISO 14496-2 (Video), e.g. Advanced Simple Profile (ASP), as followed by XviD, DivX5, 3ivx... </li></ul></ul><ul><ul><li>ISO 14496-3 (Audio), Advanced Audio Coding (AAC) </li></ul></ul><ul><ul><li>ISO 14496-10 (Video), Advanced Video Coding (AVC), also known as H.264 </li></ul></ul><ul><ul><li>ISO 14496-14 (Container), MP4 container format (uses the .mp4 extension) </li></ul></ul><ul><ul><li>ISO 14496-17 (Subtitles), MPEG-4 Timed Text subtitle format </li></ul></ul>Vision08, 03.2008 Maintaining Quality in File Based
    23. 23. AVC: AVC / H.264 Profiles <ul><li>The AVC/H.264 standard defines four different Profiles: Baseline, Main, Extended and High Profile (which themselves are subdivided into Levels): </li></ul><ul><ul><li>Baseline Profile offers I/P-Frames, supports progressive and CAVLC only </li></ul></ul><ul><ul><li>Extended Profile offers I/P/B/SP/SI-Frames, supports progressive and CAVLC only </li></ul></ul><ul><ul><li>Main Profile offers I/P/B-Frames, supports progressive and interlaced, and offers CAVLC or CABAC </li></ul></ul><ul><ul><li>High Profile (aka FRExt) adds to Main Profile: 8x8 intra prediction, custom quantisation, lossless video coding, more component formats (4:4:4) </li></ul></ul>Vision08, 03.2008 Maintaining Quality in File Based
    24. 24. AVC: Benefits <ul><li>Is an “open standard”, compared to closed formats, like Microsoft's Windows Media </li></ul><ul><li>Performs significantly better than any prior standard can, under a wide variety of circumstances in a wide variety of application environments </li></ul><ul><li>H.264 can often perform radically better than MPEG-2 video—typically obtaining the same quality at half of the bit rate or less </li></ul><ul><li>Can be carried by MPEG-2 Transport Streams making it increasingly used in HD VoD applications. </li></ul><ul><li>AVC-Intra is a Panasonic P2 implementation of Intra frame coded AVC. Gaining popularity for acquisition and editing. </li></ul>Vision08, 03.2008 Maintaining Quality in File Based
    25. 25. DNxHD/VC-3 <ul><li>Avid’s DNxHD is a HD codec technology engineered to create mastering-quality HD media at reduced bit rates to allow HD editing and production using SD infrastructure. </li></ul><ul><li>In January 08 it was approved to be compliant with SMPTE 2019 VC-3 </li></ul><ul><li>There is support from EVS and Omneon amoungst others for playout. </li></ul><ul><li>Image © Avid.com </li></ul>Vision08, 03.2008 Maintaining Quality in File Based
    26. 26. DNxHD <ul><li>Key benefits </li></ul><ul><ul><li>Optimal mastering picture quality </li></ul></ul><ul><ul><li>Reduced storage requirements </li></ul></ul><ul><ul><li>Enables real-time HD sharing and collaboration </li></ul></ul><ul><ul><li>Improved multi-stream performance </li></ul></ul><ul><ul><li>Specifically engineered for multi-generation compositing and post production </li></ul></ul><ul><ul><li>Full frame raster sampling </li></ul></ul><ul><ul><li>Choice of 8- or 10-bit sampling as well as three user-selectable bit rates </li></ul></ul><ul><ul><li>Open standard: HD Codec source code is licensable free of charge </li></ul></ul>Vision08, 03.2008 Maintaining Quality in File Based
    27. 27. Apple Pro Res 422 <ul><li>Unlike DNxHD, ProRes 422 provides full functionality at advanced resolutions (2K and 4K cinema) and SD. </li></ul><ul><li>It is DCT based, and is therefore simpler to decode than distribution oriented formats like H.264. </li></ul><ul><li>Full-width 1920x1080 and 1280x720 </li></ul><ul><li>4:2:2 chroma sampling </li></ul><ul><li>8 and 10-bit sample depth </li></ul><ul><li>I frame-only encoding </li></ul><ul><li>Variable bit-rate (VBR) encoding </li></ul><ul><li>Normal 145 Mbit/s and High-Quality 220 Mbit/s for HD resolution </li></ul><ul><li>Normal 42 Mbit/s and High-Quality 63 Mbit/s for SD resolution </li></ul><ul><li>Fast encoding and decoding (both at full size and half size) </li></ul>Vision08, 03.2008 Maintaining Quality in File Based
    28. 28. Wrappers <ul><li>Ingest and Playout are in transition </li></ul><ul><ul><li>Analogue to Compressed Digital </li></ul></ul><ul><li>Methods of storing video are changing </li></ul><ul><ul><li>Tape to File based stored on Server </li></ul></ul><ul><li>Many different new formats </li></ul><ul><ul><li>Terrestial, Satellite, Cable, VoD, IPTV </li></ul></ul><ul><ul><li>QCIF, CIF,SD, HD, </li></ul></ul><ul><ul><li>MPEG-2, MPEG-4, H.264/AVC, VC-1 </li></ul></ul><ul><ul><li>Different bitrates, GOP, Audio etc </li></ul></ul><ul><li>Many different wrappers </li></ul><ul><ul><li>MPEG TS </li></ul></ul><ul><ul><li>MXF </li></ul></ul><ul><ul><li>QuickTime </li></ul></ul>Vision08, 03.2008 Maintaining Quality in File Based
    29. 29. MXF – Wrapper <ul><li>Media eXchange Format </li></ul><ul><li>Developed as a global wrapper format for all video, audio and metadata </li></ul><ul><li>Specification is layered. “OP1A” configuration is most commonly used today (simplest implementation of MXF) </li></ul><ul><li>File interchange for networked AV file distribution </li></ul><ul><li>Format independent </li></ul><ul><ul><li>Picture Size </li></ul></ul><ul><ul><li>Interlaced or Progressive </li></ul></ul><ul><ul><li>Audio Sampling Rates </li></ul></ul><ul><li>Wraps all formats </li></ul><ul><ul><li>Current and future formats </li></ul></ul><ul><ul><li>Metadata only files allowed </li></ul></ul><ul><ul><li>Compressed and uncompressed </li></ul></ul>Vision08, 03.2008 Maintaining Quality in File Based
    30. 30. QuickTime – Wrapper <ul><li>QuickTime is a multimedia technology developed by Apple, capable of handling various formats of digital video, sound, text, animation, music, and immersive panoramic (and sphere panoramic) images </li></ul><ul><li>Openly documented and available for anyone to use royalty-free </li></ul><ul><li>The most recent version is 7 </li></ul><ul><li>Now features complete MPEG-4 compliance, and support for H.264/MPEG-4 AVC codec </li></ul><ul><li>Fifth generation iPod decodes H.264 wrapped as QuickTime </li></ul>Vision08, 03.2008 Maintaining Quality in File Based
    31. 31. Challenges of File Based Video Quality Control
    32. 32. Video Quality Control <ul><li>Video QC is a delivery requirement by many broadcasters. QC Operators would be looking at: </li></ul><ul><ul><li>Black and white level </li></ul></ul><ul><ul><li>RGB Gamut and possibly composite gamut </li></ul></ul><ul><ul><li>Number of audio channels, level and loudness peaks, phase </li></ul></ul><ul><ul><li>Picture action and graphic safe areas in all deliverable aspect ratios </li></ul></ul><ul><ul><li>Creative quality and attached metadata such as program duration, commercial breaks and clock details </li></ul></ul><ul><ul><li>Video blanking </li></ul></ul><ul><ul><li>Timecode pressence and continuity </li></ul></ul><ul><ul><li>General picture quality, standards conversion and compression artefacts, tape drop out </li></ul></ul>Vision08, 03.2008 Maintaining Quality in File Based
    33. 33. File-based video testing ‘abstraction stack’ Vision08, 03.2008 Maintaining Quality in File Based Increasing abstraction Level of video abstraction stack File organization and structure Video and audio quality Broadcast play-out center requirements Video & audio elementary stream MPEG-2 Transport Stream Baseband digital Analog signals Level of video abstraction stack Types of checks/tests File organization and structure File associations, meta-data Video and audio quality Subjective assessments and objective measurements Broadcast play-out centre requirements Measurable limitations to be suitable for transmission Video & audio elementary stream Syntactical/logical checks MPEG-2 Transport Stream Compressed representation – abstracted time Baseband digital Direct timed correlation to physical signals Analog signals Physical signal, direct measurements
    34. 34. QC from an “analogue” perspective <ul><li>Standard analogue signal tests: </li></ul><ul><ul><li>presence and level of synchronisation signals </li></ul></ul><ul><ul><li>video gamut, signal legality </li></ul></ul><ul><ul><li>audio levels </li></ul></ul><ul><ul><li>line and frame timings </li></ul></ul><ul><li>Standard solutions: </li></ul><ul><ul><li>waveform monitors </li></ul></ul><ul><ul><li>PPM/VU audio meters </li></ul></ul>Vision08, 03.2008 Maintaining Quality in File Based
    35. 35. Baseband Digital (SDI) <ul><li>No direct correlation to analogue signal, e.g. </li></ul><ul><ul><li>video data needs to be extracted to re-construct ‘analogue’ signal </li></ul></ul><ul><ul><li>synchronization ‘signals’ are code-words in data stream </li></ul></ul><ul><li>Example SDI errors: </li></ul><ul><ul><li>signal jitter, level errors – bits misinterpreted </li></ul></ul>Vision08, 03.2008 Maintaining Quality in File Based
    36. 36. Structure of MPEG-2 Transport Streams <ul><li>Inside packetization and CRC data of MPEG-2 TS: </li></ul><ul><li>Video and audio data can be tens or hundreds of Mbytes – interleaved in time through-out the MPEG-2 TS packets </li></ul>Vision08, 03.2008 Header PID CRC Video Elementary Stream Audio Elementary Stream Meta- data Transport Stream data - tables, etc. Maintaining Quality in File Based 188 byte packets (or 204 bytes) Video Audio Tables Meta-data
    37. 37. Elementary Streams <ul><li>Video and audio compression separate from TS </li></ul><ul><ul><li>complex </li></ul></ul><ul><ul><ul><li>and increasingly so with MPEG-4/AVC </li></ul></ul></ul><ul><ul><li>generate their own types of errors </li></ul></ul><ul><li>Legal TS can have incorrect/illegal ES within </li></ul>Vision08, 03.2008 PID CRC Video Elementary Stream bit errors during encoding Maintaining Quality in File Based 188 byte packets (or 204 bytes)
    38. 38. Elementary stream Bit Error Example <ul><li>A single bit error in a single block in a single frame </li></ul><ul><li>NOT spotted in play-out centre </li></ul><ul><ul><li>despite a ‘full’ QC being done i.e. </li></ul></ul><ul><ul><ul><li>base-band tests </li></ul></ul></ul><ul><ul><ul><li>TS tests </li></ul></ul></ul><ul><ul><ul><li>visually watched by QC personnel </li></ul></ul></ul>Vision08, 03.2008 Maintaining Quality in File Based
    39. 39. Bit Error Example continued <ul><li>Error smoothed over by the advanced decoder in play-out centre </li></ul><ul><ul><li>Set-top box crashed </li></ul></ul><ul><ul><li>broadcaster thought end-customers were having ‘finger trouble’ </li></ul></ul><ul><li>Playing the clip does not guarantee encoding </li></ul><ul><ul><li>Professional decoder has large buffer </li></ul></ul><ul><ul><li>Decoder may “mask” errors </li></ul></ul><ul><ul><li>Bitrate, GOP interval, colour sample configuration cannot be seen </li></ul></ul><ul><li>The syntax of the compression must be checked </li></ul><ul><li>Errors detailed in the report from Tektronix Cerify </li></ul>Vision08, 03.2008 Maintaining Quality in File Based
    40. 40. Good but still no good <ul><li>Legal and syntactically correct - but not correct for the broadcaster: </li></ul><ul><ul><li>broadcaster wants 720x 608 resolution to include some of the vertical interval but the video has been supplied/encoded at 720x 576 </li></ul></ul><ul><ul><li>English audio is required to be on channels 1 & 2 (Spanish on 3 & 4) but these have been swapped </li></ul></ul><ul><ul><li>the peak bit-rate should be 4.5 Mb/s, but actually goes to 4.6Mb/s </li></ul></ul><ul><ul><li>The MPEG is sampled 4:2:0 instead of 4:2:2 </li></ul></ul><ul><li>These are issues that are very difficult to “see” by the QC operator </li></ul>Vision08, 03.2008 Maintaining Quality in File Based
    41. 41. File Based video Quality Control <ul><li>File Based Video QC Application Challenges </li></ul><ul><ul><li>Traditional video T&M only checks baseband (luma/chroma/signal) levels in analogue and digital video streams </li></ul></ul><ul><ul><li>File-based video is different. It must be checked for </li></ul></ul><ul><ul><ul><li>Correct Encoding Syntax – at digital level, audio/video must be encoded without errors, so it plays out correctly at the Customer’s STB / playout device </li></ul></ul></ul><ul><ul><ul><li>Correct Parameters – audio/video bitrates, GOP structure, Color-space, Color depth, Frame size, Frame rate, Aspect ratio, Quantization levels </li></ul></ul></ul><ul><ul><ul><li>Correct Baseband and Quality levels - analog parameters for Signal levels, Luma, Chroma, Gamut and Quality levels of Black frames, Blockiness, Loss of audio, Audio clipping, Video/Audio playtime </li></ul></ul></ul>Vision08, 03.2008 Maintaining Quality in File Based
    42. 42. Human Quality Control Challenges <ul><li>Human QC/play-out testing is time consuming and expensive </li></ul><ul><li>Visual/audio errors are easily missed with human play-out </li></ul><ul><ul><li>just by blinking or losing concentration for a second </li></ul></ul><ul><ul><li>different skill level/experience/training of testers </li></ul></ul><ul><li>Simple errors – human may not get constraints correct </li></ul><ul><li>Consistency – Cannot repeat exactly the same test on content, day after day, week after week </li></ul><ul><li>Person cannot easily look inside the file for example: </li></ul><ul><ul><li>standard used for compression for video, audio </li></ul></ul><ul><ul><li>bit-rates of video, audio and overall </li></ul></ul><ul><ul><li>visual quality ... </li></ul></ul>Vision08, 03.2008 Maintaining Quality in File Based
    43. 43. Automatic Quality Control for File Based Video
    44. 44. Broadcast technical challenges Vision08, 03.2008 <ul><li>Broadcasting Key Challenges </li></ul><ul><li>Reliably store, aggregate and distribute more content in more formats for new distribution paths </li></ul><ul><li>Mastering New Technologies: </li></ul><ul><li>File based Workflow </li></ul><ul><li>HD, H.264, MPEG4, VC1, VOD, Video over IP </li></ul><ul><li>Challenges </li></ul><ul><li>Explosion of content and formats </li></ul><ul><li>Need to QC ingested content from multiple sources </li></ul><ul><li>Human QC not sufficient and not 24/7 </li></ul>Content Delivery Ingest Servers Edit, Schedule & Monitor Playout Servers Terrestrial VOD IPTV Archive News Feeds Sport Movies Post production File based workflow Satellite Auto QC Maintaining Quality in File Based Ingest Edit Schedule Playout
    45. 45. File-based Auto QC at ingest Vision08, 03.2008 Automation / Asset Management System Video servers GigE LAN Ingest API Auto QC Controller Auto QC Test Unit Auto QC Test Unit Auto QC Test Unit User Web GUI Maintaining Quality in File Based
    46. 46. Vision08, 03.2008 File-based Auto QC at ingest Quality Control units Video Servers Automation Maintaining Quality in File Based
    47. 47. File-based Auto QC at Turner <ul><li>Turner Broadcasting </li></ul><ul><ul><li>Location: Atlanta, GA </li></ul></ul><ul><ul><li>One of world’s largest broadcasters </li></ul></ul><ul><li>Content </li></ul><ul><ul><li>News </li></ul></ul><ul><ul><li>Shows </li></ul></ul><ul><ul><li>Cartoons </li></ul></ul><ul><ul><li>Movies </li></ul></ul><ul><li>Format </li></ul><ul><ul><li>Mostly MPEG-2 SD 5-25Mb/s </li></ul></ul><ul><ul><li>Moving to HD and MXF </li></ul></ul><ul><ul><li>Pioneers of MXF AS02 </li></ul></ul><ul><li>Existing QC </li></ul><ul><ul><li>QC personnel sample batches of content </li></ul></ul><ul><ul><li>3x 8hr Shifts/day </li></ul></ul><ul><ul><li>Rely on some content being checked at source </li></ul></ul>Vision08, 03.2008 Maintaining Quality in File Based
    48. 48. File-based Auto QC at Turner <ul><li>Requirement </li></ul><ul><ul><li>Need to cover 12 channels of content </li></ul></ul><ul><ul><li>Initially to supplement then </li></ul></ul><ul><ul><li>Eventually to replace manual QC </li></ul></ul><ul><ul><li>Each up to 24hrs of new material / day per channel </li></ul></ul><ul><li>Video Servers </li></ul><ul><ul><li>Omneon Spectrum </li></ul></ul><ul><li>Automation </li></ul><ul><ul><li>ProBel Morpheus Asset Management </li></ul></ul><ul><li>Quality Control </li></ul><ul><ul><li>12x Tek Cerify units at ingest </li></ul></ul><ul><ul><li>Integrated using CeriTalk with Probel Morpheus </li></ul></ul><ul><ul><li>Installed July 07 – Feb 08 </li></ul></ul>Vision08, 03.2008 Maintaining Quality in File Based
    49. 49. File-based Auto QC at SBS <ul><li>SBS </li></ul><ul><ul><li>Broadcasts to Denmark, Sweden, Netherlands, Luxemburg, Greece, Poland, Bulgaria, Germany </li></ul></ul><ul><ul><li>40M viewers </li></ul></ul><ul><ul><li>Expanding services to Scandinavia and Eastern Europe </li></ul></ul><ul><ul><li>Broadcast Playout Centre in London </li></ul></ul><ul><li>Content </li></ul><ul><ul><li>Currently SD MXF wrapped MPEG-2 </li></ul></ul><ul><ul><li>Moving to HD and MXF </li></ul></ul><ul><li>Requirements </li></ul><ul><ul><li>800 - 1000 hrs of content/week </li></ul></ul><ul><ul><li>Auto QC of ingested files from multiple providers </li></ul></ul><ul><ul><li>Expansion capability to HD </li></ul></ul><ul><ul><li>Fully automated broadcast flow </li></ul></ul>Vision08, 03.2008 Maintaining Quality in File Based
    50. 50. File-based Auto QC at SBS <ul><li>Solution </li></ul><ul><ul><li>Systems Integrator: Wellen & Noethen </li></ul></ul><ul><ul><li>Asset Management system: S4M </li></ul></ul><ul><ul><li>Video Servers: GVG K2 </li></ul></ul><ul><ul><li>Auto QC: Tektronix Cerify – cluster of 5 units integrated with the asset management system </li></ul></ul><ul><li>Status </li></ul><ul><ul><li>Went live Sept 07 </li></ul></ul><ul><ul><li>Currently around 800hrs per week of 24/7 auto QC </li></ul></ul><ul><ul><li>Backed by some manual rechecking of content identified by the auto QC as having problems </li></ul></ul>Vision08, 03.2008 Maintaining Quality in File Based
    51. 51. File-based Auto QC at JCA Vision08, 03.2008 <ul><li>UK based broadcast services </li></ul><ul><ul><li>Encode and Format wide range of file based video </li></ul></ul><ul><ul><li>For international broadcasters and production companies world wide </li></ul></ul><ul><li>Requirement </li></ul><ul><ul><li>Reliable QC that could run automatically </li></ul></ul><ul><ul><li>Integrated into a file-based workflow </li></ul></ul><ul><ul><li>Needed to be suitable for many different formats </li></ul></ul><ul><li>Status </li></ul><ul><ul><li>Cerify Auto QC </li></ul></ul><ul><ul><li>Around 10 – 50 hrs/week </li></ul></ul>Maintaining Quality in File Based
    52. 52. In Conclusion <ul><li>Video is moving to file-based workflows </li></ul><ul><li>File-based video can be in several different compression formats and wrappers </li></ul><ul><li>New compression types are more complex than MEPG-2 and give much greater scope for errors </li></ul><ul><li>Errors typically occur separately in the Elementary Streams as well as in the meta-data - that is, there could be a perfectly legal and correct Transport Stream, but the video or audio Elementary Stream or meta-data is incorrect. </li></ul><ul><li>File-based video quality control presents significant challenges for human quality control </li></ul><ul><li>Automatic Quality control supplemented by some manual rechecking has now been successfully implemented at broadcasters in US and Europe </li></ul>Vision08, 03.2008 Maintaining Quality in File Based
    53. 53. Questions?

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