[FFmpeg-user] AVC3 -> AVC1 conversion

[Moritz Barsnick]

On Sun, Nov 26, 2017 at 17:27:05 -0500, antony baxter wrote:
> I've recently received some H264 videos marked as AVC3:
[...]
>     Stream #0:1(und): Video: h264 (Main) (avc3 / 0x33637661), yuvj420p(pc, bt709), 704x396 [SAR 1:1 DAR 16:9], 819 kb/s, 25 fps, 25 tbr, 25k tbn, 50 tbc (default)

> I can obviously convert them into H264 avc1 the long way, but wondered if
> there was a quick way of simply changing the metadata of the avc3 stream
> into avc1?

ffmpeg never just modifies the original, it at least demuxes and
remuxes. It doesn't need to reencode "the long way" though.

I'm sure there are tools out there to modify the FourCC by just
fiddling with a few bytes.

Anyway, you could try to remux using ffmpeg instead of re-encoding:

$ ffmpeg -i inputvideo -map 0 -c copy outputvideo.mp4

If that happens to retain the avc3 tag, add the option "-tag:v avc1".

Moritz