[FFmpeg-devel] [PATCH] Handle AVID MJPEG streams directly in the MJPEG decoder.

[James Almer]

On 2/27/2021 1:33 PM, Michael Niedermayer wrote:
> On Wed, Feb 24, 2021 at 11:25:42AM +0100, Anton Khirnov wrote:
>> AVID streams - currently handled by the AVRN decoder - can be (depending
>> on extradata contents) either MJPEG or raw video. To decode the MJPEG
>> variant, the AVRN decoder currently instantiates a MJPEG decoder
>> internally and forwards decoded frames to the caller (possibly after
>> cropping them).
>>
>> This is suboptimal, because the AVRN decoder does not forward all the
>> features of the internal MJPEG decoder, such as direct rendering.
>> Handling such forwarding in a full and generic manner would be quite
>> hard, so it is simpler to just handle those streams in the MJPEG decoder
>> directly.
>>
>> The AVRN decoder, which now handles only the raw streams, can now be
>> marked as supporting direct rendering.
>>
>> This also removes the last remaining internal use of the obsolete
>> decoding API.
>> ---
>> And now without the missing isom tag change. Thanks to Andreas for noticing.
>> ---
>>   configure               |  1 -
>>   libavcodec/avrndec.c    | 71 +----------------------------------------
>>   libavcodec/mjpegdec.c   | 11 +++++++
>>   libavcodec/version.h    |  2 +-
>>   libavformat/avidec.c    |  6 ++++
>>   libavformat/isom_tags.c |  4 +--
>>   tests/fate/video.mak    |  2 +-
>>   7 files changed, 22 insertions(+), 75 deletions(-)
> 
> breaks:
> ./ffmpeg -vlowres 2 -i ~/tickets/162/avid.avi  -vframes 3 avrn.avi
> 
> The outputed image is several times bigger and looks as if it encodes random bits od memory

Can you try again with git head? I removed the max_lowres value since 
the avrn raw decoder doesn't support it, since it was pulled from the 
mjpeg version.

> 
> thx
> 
> [...]
> 
> 
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