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

[Gyan]

On Mon, Jul 24, 2017 at 11:56 PM, Ute Willmore <uwillmore at remotegeo.com>
wrote:

> Hi everyone,
>
> I am hoping someone on this list can help me with a problem I am having
> when converting a .avi video to .mp4 using FFmpeg. The output I get starts
> out looking good, but then degrades and by the time the 18 second video
> finishes it is hard to recognize what's on the screen. The colors are all
> off, some areas are just single color blobs where there used to be trees.
>

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.

So I ran

mp4box -aviraw video hd.avi

which produced hd_video.h264. This plays fine with ffplay.

Running

ffmpeg  -v verbose -i hd_video.h264 -i hd.avi -map 0 -map 1:a -vf
scale=640:480 out.mp4

produces an undistorted output.

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.