[Libav-user] MJPEG quantization tables

Carl Eugen Hoyos cehoyos at ag.or.at
Fri Dec 11 00:18:31 CET 2015

On Wednesday 15 July 2015 11:09:30 am Michael Toon wrote:
> Hello,
> I am using the encoder libs to encode MJPEG video which I am packaging up
> to send via RTP.  The encoded bit stream that I generate only appears to
> have a single quantization table defined, however the RTP payload format
> specifies that if using custom quantization tables there should be two
> separate quantization tables for luma and chroma. Having separate tables
> seems to make sense to try and gain most encoding efficiency, especially
> since I need to transmit two tables regardless. Is there a reason why the
> MJPEG codec only generates a single table,

> is there an option that I can to use separate tables?

There is now the option "-force_duplicated_matrix 1" to force writing 
two JPEG tables, even if they are identical.

Hope that helps, Carl Eugen

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