[FFmpeg-user] AAC track copy problem in mp4

[Dennis]

Maybe try demuxing it with MP4Box, resize with FFmpeg, then remux with
MP4Box?
http://gpac.wp.mines-telecom.fr/downloads/gpac-nightly-builds/


On Fri, Feb 6, 2015 at 10:37 AM, Petr Tresnak <peter.cherry at quick.cz> wrote:

> Hi all,
> I downscale the following 4k to 1080 using ffmpeg -i 4k.mp4 -vf
> scale=1920:1080 -c:v libx264 -preset fast -crf 18 -c:a copy output.mp4"
>
> Duration: 00:00:10.56, start: 0.080000, bitrate: 95904 kb/
> Stream #0:0(und): Video: h264 (High) (avc1 / 0x31637661), yuvj420p(pc,
> bt709), 3840x2160 [SAR 1:1 DAR 16:9], 95655 kb/s, 25 fps
> Stream #0:1(und): Audio: aac (mp4a / 0x6134706D), 48000 Hz, stereo, fltp,
> 124 kb/s (default)
>
> But there is a problem with proper copy of audio track:
>
> [mp4 @ 05e30860] track 1: codec frame size is not set
> [mp4 @ 05e30860] Packet with invalid duration -1024 in stream 1
>
> In trans-coded video file there is a small difference in audio afterwards
> (AAC vs AAC LC, bitrate 124 vs 125):
> Stream #0:1(und): Audio: aac (LC) (mp4a / 0x6134706D), 48000 Hz, stereo,
> fltp, 125 kb/s (default)
>
> Can you help how to force ffmpeg to copy audio track?
> Thanks
> Peter
>
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