[FFmpeg-devel] [PATCH] avformat/mux: skip parameter and pts checks for data muxer

[Gyan]

On 28-04-2019 04:15 PM, Nicolas George wrote:
> Gyan (12019-04-28):
>> Corrupt streams in sufficiently intact containers (MP4, TS) so they can be
>> demuxed but decoder context fields are incomplete/invalid, so ffmpeg won't
>> streamcopy-mux them.
>>
>> Depending on the exact situation, I would use a repair or analysis tool to
>> check them or supply an alternate esds..etc
> And you want to just dump the packets payload in a file? With the ffmpeg
> command-line?
>
> Then I suggest to implement that as a ffmpeg option:
>
> 	ffmpeg -dump_stream:0 stream0.bin -i damaged.mp4 -f null -
I'll try this but I don't think the command as presented will work because

a) there's no codec option set, so ffmpeg has to decode frames and that 
will fail for damaged streams. But this can be quickly remedied by 
adding -c copy

b) ffmpeg will call avformat_write_header for the output, which will 
likely fail because of the aforementioned codec parameter issues. When 
that happens, ffmpeg will exit and only the packets demuxed and flushed 
up to that point will be present in the dumped file. This could possibly 
be averted by providing a valid dummy input and mapping only that to the 
output. However, I believe ffmpeg will then exit when that output is 
marked as finished, but the dumped stream may not be because the main 
transcode() loop isn't sensitive to it.

The pipeline for dumping damaged streams is identical to dumping valid 
streams except for the part when timestamps are regulated and codec 
fields validated for the target muxer, which is what my patch disables 
for a single muxer that doesn't need them. I don't see much (any?) 
"wasted" processing with my patch, relative to streamcopying a valid stream.

Gyan