[FFmpeg-user] Poor quality output when converting avi to mp4

[Ute Willmore]

Thank you Moritz! I will at least consider doing that, but I was beginning
to suspect a bug myself. I just need to find a solution or work around
first before I can take the time to do some more testing with VLC to
confirm a bug. VLC allows you to use ffmpeg to convert a video from the
command line and I want to see what the output looks like before I report a
bug.

Ute

On Mon, Jul 24, 2017 at 2:05 PM, Moritz Barsnick <barsnick at gmx.net> wrote:

> On Tue, Jul 25, 2017 at 00:25:36 +0530, Gyan wrote:
> > Running your conversion command on your source, I see
> >
> > Input stream #0:0 (video): 856 packets read (18695093 bytes); 104 frames
> > decoded;
> >
> > Muxing to TS and playing that throws invalid NAL warnings.
>
> But that was a conversion, right?
>
> > mp4box -aviraw video hd.avi
> >
> > which produced hd_video.h264. This plays fine with ffplay.
>
> That was remuxing, right?
>
> > As best as I can tell, ffmpeg does have issues with parsing non-standard
> > H.264 bitstreams. It's certainly not as resilient as other decoders.
>
> I did a different test:
> - Playing the original video with ffplay produces the peculiar image
>   Ute is probably seeing.
> - Playing with mplayer produces an acceptable image. (mplayer uses
>   ffmpeg's libavcodec for decoding the video..)
> - Playing with "mplayer -demuxer lavf" produces the same junk as
>   ffplay.
>
> So I come to the conclusion that ffmpeg/libavformat has an issue
> demuxing the file. mplayer's native AVI demuxer doesn't. The latter is
> also probably valid for VLC, if that works for Ute. mp4box also doesn't
> have an issue. So, I think this is worth tracking as an ffmpeg bug (on
> trac.ffmpeg.org), providing the sample as an attachment, the command
> line and the complete, uncut console output.
>
> My $0.02,
> Moritz
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