Doom9's Forum - View Single Post - Convert an h264/mp3 video for DVD playback

manolito · 20th January 2016, 14:28

You really need to do some reading to understand the basic concepts of video encoding. Some buzzwords are Discrete Cosine Transformation (DCT), Quantization and of course Quantization Matrices.

I found this old thread very helpful:
http://forum.doom9.org/showthread.ph...91#post1465291

Specifying a quantizer value influences all frequencies the same way. With a Quantization Matrix the quantizer is modified depending on the frequency. This way it is possible for example to use a higher quantization for high frequencies (high detail, lots of movement) and a lower quantization for dark and static scenes. In such a matrix the lower frequencies are represented by the values on top and to the left, while the values at the bottom and to the right represent the higher frequencies.

The HCenc PDF manual has a matrix section where you can see a lot of the popular MPEG2 matrices. If you do not specify a matrix for the encode, every encoder will use a default matrix, but this can be different for different encoders.

FFMpeg uses the MPEG Standard matrix by default (the one where all non-intra coefficients are 16). This is a bad idea for DVD compliant encodes, the normal MPEG matrix (sometimes called MPEG Adapted) is a much better choice.

Modern encoders like CCE or HCenc can adapt the matrix they use on the fly during the encode (in HCenc the parameter is called AQM). Some experts say that (at least for encoders which use an exponential quantizer scale like CCE or HC) the influence of custom quant matrices on the encoding quality is overrated. Please read the dispute between Dark Shikari and Manono in the old thread I linked to.

Cheers
manolito

20th January 2016, 14:28	#14 \| Link
manolito Registered User Join Date: Sep 2003 Location: Berlin, Germany Posts: 3,079	You really need to do some reading to understand the basic concepts of video encoding. Some buzzwords are Discrete Cosine Transformation (DCT), Quantization and of course Quantization Matrices. I found this old thread very helpful: http://forum.doom9.org/showthread.ph...91#post1465291 Specifying a quantizer value influences all frequencies the same way. With a Quantization Matrix the quantizer is modified depending on the frequency. This way it is possible for example to use a higher quantization for high frequencies (high detail, lots of movement) and a lower quantization for dark and static scenes. In such a matrix the lower frequencies are represented by the values on top and to the left, while the values at the bottom and to the right represent the higher frequencies. The HCenc PDF manual has a matrix section where you can see a lot of the popular MPEG2 matrices. If you do not specify a matrix for the encode, every encoder will use a default matrix, but this can be different for different encoders. FFMpeg uses the MPEG Standard matrix by default (the one where all non-intra coefficients are 16). This is a bad idea for DVD compliant encodes, the normal MPEG matrix (sometimes called MPEG Adapted) is a much better choice. Modern encoders like CCE or HCenc can adapt the matrix they use on the fly during the encode (in HCenc the parameter is called AQM). Some experts say that (at least for encoders which use an exponential quantizer scale like CCE or HC) the influence of custom quant matrices on the encoding quality is overrated. Please read the dispute between Dark Shikari and Manono in the old thread I linked to. Cheers manolito Last edited by manolito; 20th January 2016 at 14:30.