Mpeg For The Media Sonic Players


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  • Note:
    Hardware encoders like the Tandberg reduce the color resolution to 4.2.0 but it is possible to encode and play back at 4.2.2. using the Lucent or a software encoder.
    4.2.0 has the same horizontal color resolution as 4.2.2 but half the vertical color resolution.
  • Talk about GOP size and effect on high motion sources.
  • Mpeg For The Media Sonic Players

    1. 1. A Division of Electrosonic MPEG for the MediaSonic Players Orlando Moreno 408.656.2498
    2. 2. Only what you need to know! Equation 1: Forward Discrete Cosine Transform 408.656.2498
    3. 3. MPEG only what you need to know! • MPEG is a compression standard, currently we use MPEG2 on the Players. • An MPEG file contains Video and Audio in discrete streams called ELEMENTARY streams. Time stamps are used to synchronize the streams. • These streams are MULTIPLEXED together either as a PROGRAM or TRANSPORT stream. • This is all bad news! 408.656.2498
    4. 4. Program / Transport • Electrosonic SD Player uses MPEG2 Program Streams that are designed for storage and playback from disk. • MediaSonic DTV Players use MPEG2 Transport Streams designed for transmission over communication systems like ATM and broadcast. They are designed to recover from error not perfect playback! 408.656.2498
    5. 5. MPEG Encoder Audio Data Video Data Mpeg Encode Mpeg Encode Multiplexer System Clock Multiplexed Stream Audio PES Packet Video PES Packet 408.656.2498
    6. 6. Hardware MPEG Video Encoder 4.2.0 @ 8bit4.2.2 @ 10bit HDSDI DCT D5 is 4.2.2 – 10 bit HDCAM is 3.1.1 - 8 bit 408.656.2498
    7. 7. Color Sampling Standards PBPBPBPB PR PR PR PR Y Y Y Y Y Y Y Y PBPBPBPB PR PR PR PR Y Y Y Y Y Y Y Y Line 1 Line 2 PBPBPBPB PR PR PR PR Y Y Y Y Y Y Y Y Line 1 Line 2 Y Y Y Y Y Y Y Y 4.2.2 4.2.0 408.656.2498
    8. 8. Video Compression I Frame B Frames P Frames Group of Pictures in Encoder Sequence 408.656.2498
    9. 9. Headers Sequence Header GOP Header Group of Pictures 408.656.2498
    10. 10. Video - Things to remember. • GOP is usually half a second long, so 15 frames for NTSC and 12 for PAL. • A ‘Closed’ GOP is better for random access and synchronous files. • Each GOP should contain a Sequence header. • Files should start on a Sequence header. 408.656.2498
    11. 11. Audio Compression • MediaSonic currently only support Dolby AC3 Audio streams. • The standard allows for other types of audio including MPEG layer 2 audio that is created by some software encoders (Heuris). • AC3 packets are 32msec long. 408.656.2498
    12. 12. AC3 Audio • A compression scheme that can carry anything from mono to 5.1 surround sound. We typically use it in either stereo or 5.1. • The stereo output plays back a mix of the AC, although we usually only encode stereo since HW encoders don’t support surround sound. 408.656.2498
    13. 13. Audio – Things to remember. • AC3 is the only supported audio format. • Audio needs to be encoded at 384kbits. • Audio needs to be sampled at 48kHzs. • AC3 can only exist as complete packets of 32 msecs. 408.656.2498
    14. 14. Multiplexing Time Audio Elementary Video Elementary • Wraps the audio and video into a single stream, in our case a Transport stream. 408.656.2498
    15. 15. Multiplexing • Data is packed into 188 byte packets each starting with a h47. • A well made file should start and end on packet boundaries. • Files can be viewed with a Hex viewer to check. 47 40 11 11 00 00 E4 00 00 84 C0 13 3B F4 EB E6 F1 1B F4 EB 9F BD FF FF FF FF FF FF FF FF 00 00 01 B3 E4 00 00 84 C0 13 3B F4 EB E6 F1 1B F4 EB 9F BD FF FF FF FF FF FF FF FF 00 13 3B F4 EB E6 F1 1B F4 EB 9F 00 01 B3 E4 00 00 84 C0 13 3B F4 EB E6 F1 1B F4 EB 9F BD FF FF FF FF FF FF FF FF 00 13 3B F4 84 C0 13 3B F4 EB E6 F1 1B F4 EB 9F BD FF FF FF FF FF FF FF FF 00 00 01 B3 E4 00 00 84 C0 13 3B F4 EB E6 F1 1B F4 EB 9F BD FF FF FF FF FF FF FF FF 00 13 3B F4 EB E6 F1 1B F4 EB 9F 00 01 B3 E4 00 00 84 C0 13 3B F4 EB E6 F1 1B F4 FF FF 01 B5 20 1E 47 00 11 12 Start of packet Start of Seq. head End of packet 408.656.2498
    16. 16. Mux – Things to remember. • Mux is Transport and uses 188 byte packets. • Mux data rate must allow for the Video + Audio + Overhead. • Audio should be shorter than video. • File should and start and end on packet boundaries. 408.656.2498
    17. 17. Software Encoders • There are two prominent encoders available – PixleTools - MPEGRepair. • Picture only. • Takes 24 bit/pixel graphic files only (BMP or TGA). • Easy to use & reliable. • Makes 4.2.0 or 4.2.2 files (our player auto detect and play). • Has a ‘bug’ that adds a stream terminator incorrectly in the built in multiplexer (used to make video only transport streams). – Heuris - MPP2. • Picture only or + MPEG audio (unsupported). • Takes AVI and QuickTime files (with audio). • Can window into source image. • Can take images directly from film scanners. 408.656.2498
    18. 18. Software Encoders • Make files with clean start. They include a Sequence header and first frame is always an I frame. • Make files with clean end. It is possible to make clean looping files. – Frame count = (GOP size) x N for clean looping files. • Very good for 3D work. • MPEGRepair video only files must be trimmed before use! 408.656.2498
    19. 19. Real-time Encoders • Designed to stream ASI data to a transmission system. • Data can be captured asynchronously but will need ‘trimmed’ for quality playback. • Some can be switched from ‘Video Off’ to ‘Video On’ creating a Sequence header and predictable I frame. • Can make AC3 & MPEG2 audio. – Typically Left & Right + back up L & R. 408.656.2498
    20. 20. Software Multiplexers • Manzaneta - MP2TSME – Very flexible DOS based tool. A b**** to use. • PixelTools – Transmux – Easy Windows tool but no video only option. • Both use the same Manzanita engine for Transport streams. 408.656.2498
    21. 21. MPEG for Large Screens • MPEG uses motion prediction in B and P frames! • MPEG encoding looses high frequencies! • 4.2.0 can resolve horizontal color if there are 2+ similar colored pixels in a row and vertical color if there are 2+ pixels in a column! 408.656.2498
    22. 22. MPEG for Large Screens • SD can be up-res’d to HD giving a better image than SD alone. • This allows higher bitrates than the current SD Players. • Allows for small GOP’s that better deal with fast motion vectors. 408.656.2498
    23. 23. 408.656.2498 Orlando Moreno 408.656.2498