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Video
Transcoding
& Transrating
Yossi Cohen
1
Overview
 Full Transcode
 Open Loop transraters
Coefficient Drop Transrater
Re-quantization transrater

 Closed loop ...
Full Transcoder
 Full transcoding does full encoding and
decoding of the video. Features include:
Easy Implementation
U...
Aided Transcoder
 Full decoding of the video
 Encoding Video while re-using the decoded video
information including:
Qp...
Aided Transcoder Features
 High CPU requirements
 Like Full transcoder, enables:
 Resizing
 Change of Frame type (P->I...
Open Loop Transcoders
 Open loop transcoders are fast and simple
transrater.
 Open-loop – does not correct the drift err...
Coefficient Drop Transrater
 Performs only Entropy Decoding/Encoding
 Drops some of the coefficients according to
psycho...
Re-Quanitzation transrater
 Performs Entropy decoding and dequantization followed by quantization with
an Higher Qp (lowe...
Closed loop transrater (FPDT)
 Performs Entropy decoding and dequantization followed by quantization with
an Higher Qp (l...
Closed Loop Transrater - Features
 Faster then Transcoders
 No drift
 Quality is transcoder grade per same bitrate

10
Quality / CPU comparison
 Line – Quality, Bar – CPU Cycles

Coefficient
Drop

Re-Quantization
transrater

FPDT

Aided Tra...
Frame dropping overview
 Frame dropping could improve KPI (5-10%)
and reduce CPU load.
 Smooth frame drop – convert to a...
Frame Dropping -2
 Transcoders support both Regular frame
drop
 Transraters only supports limited fps frame
drop
 FPDT ...
Frame Resize
 Frame Resize could considerably lower
bitrate.
 CPU - Requires per pixel operations for
resizing – higher ...
Thank you!
More About me:
 Video Expert
 Lectures on Video / Android / VoIP
 Android Native Developer

Yossi Cohen
yoss...
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Video transcoding transrating

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Video Tanscoding and Transrating methods review and comparison

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Video transcoding transrating

  1. 1. Video Transcoding & Transrating Yossi Cohen 1
  2. 2. Overview  Full Transcode  Open Loop transraters Coefficient Drop Transrater Re-quantization transrater  Closed loop transrater FPDT 2
  3. 3. Full Transcoder  Full transcoding does full encoding and decoding of the video. Features include: Easy Implementation Usually used for  format conversion such as MPEG2 Video->H264  Video Resize and frame rate reduction Highest CPU requirements 3
  4. 4. Aided Transcoder  Full decoding of the video  Encoding Video while re-using the decoded video information including: Qp selection Motion vectors Block size (8x8, 4x8 etc.) selection MV, Qp 4
  5. 5. Aided Transcoder Features  High CPU requirements  Like Full transcoder, enables:  Resizing  Change of Frame type (P->I, I->P) for sync point changing  Smooth frame rate conversion  Accurate (no drift) transcoding 5
  6. 6. Open Loop Transcoders  Open loop transcoders are fast and simple transrater.  Open-loop – does not correct the drift error created by the transrating on next frames  Introduces drift error into the video – video quality seriously degrades as a function of the distance from last I frame. 6
  7. 7. Coefficient Drop Transrater  Performs only Entropy Decoding/Encoding  Drops some of the coefficients according to psycho-visual models.  Features  Fastest transrater  Poorest video quality per bitrate  Introduce drift 7
  8. 8. Re-Quanitzation transrater  Performs Entropy decoding and dequantization followed by quantization with an Higher Qp (lowers quality & BR)  Features  Fast Transrater  Poor video quality per bitrate  Introduce drift 8
  9. 9. Closed loop transrater (FPDT)  Performs Entropy decoding and dequantization followed by quantization with an Higher Qp (lowers quality & BR)  Adds quantization error from previous frame to next frame to avoid drift Error Store 9
  10. 10. Closed Loop Transrater - Features  Faster then Transcoders  No drift  Quality is transcoder grade per same bitrate 10
  11. 11. Quality / CPU comparison  Line – Quality, Bar – CPU Cycles Coefficient Drop Re-Quantization transrater FPDT Aided Transcoder Full Transcode 11
  12. 12. Frame dropping overview  Frame dropping could improve KPI (5-10%) and reduce CPU load.  Smooth frame drop – convert to any fps, fixed deltaT between frames, frame interpolation. Very high CPU requirements  Regular frame drop – drop any frame introduce some jerkiness  Limited fps – cant drop any frame, introduce higher jerkiness 12
  13. 13. Frame Dropping -2  Transcoders support both Regular frame drop  Transraters only supports limited fps frame drop  FPDT transrater might support regular frame drop at additional development time 13
  14. 14. Frame Resize  Frame Resize could considerably lower bitrate.  CPU - Requires per pixel operations for resizing – higher CPU but lower encoded frame size which lowers CPU.  Transcoder could easily support resize – additional CPU requirements  FPDT could support resize but would cost considerable CPU and development time 14
  15. 15. Thank you! More About me:  Video Expert  Lectures on Video / Android / VoIP  Android Native Developer Yossi Cohen yossicohen19@gmail.com http://www.mobilevideotech.com +972-545-313092 15

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