[Libav-user] MJPEG Quantization tables

Richard Hussong rhussong at westpond.com
Mon May 18 19:53:50 EEST 2020

On Mon, May 18, 2020 at 7:38 AM Виктор Мулин <17sep96 at gmail.com> wrote:

> Hello! When using the mjpeg codec to convert an image from bmp to jpg
> format, a picture with one quantization table is created. I need two
> standard tables described in the jpeg iso / iec 10918-1 T.81 standard in
> Appendix K.1 and K.2 to be added to the output image file. I also found
> them in the ffmpeg source codes (jpegtables.c -> std_luminance_quant_tbl
> and jpegtables.c -> std_chrominance_quant_tbl [url:
> https://ffmpeg.org/doxygen/trunk/jpegtables_8c_source.html]. I looked
> through the mailing list archive and found old solutions (
> https://ffmpeg.org/pipermail/libav-user/2015-July/008318.html), but now
> the av_codec_set_chroma_intra_matrix () function is declared depricated.
> How do I get what I want? How to set intra_matrix, chroma_intra_matrix and
> inter_matrix (in the description they are almost the same)?

The intra_matrix and inter_matrix can now be set directly in the
AVCodecContext structure. See
https://ffmpeg.org/doxygen/trunk/structAVCodecContext.html, and search for
"intra_matrix" and "inter_matrix".

P.S .: Sorry, I don't speak English well. I use google translator.

Don't worry - what you wrote is clear enough.

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