[FFmpeg-user] ffmpeg mux cause quality loss

[Tom Evans]

On Thu, Mar 28, 2013 at 4:11 PM, Wu, Mandy <mandy.wu at intel.com> wrote:
> Hi,
> I used below command to mux H264 video and AAC audio to a MP4 container format:
> ffmpeg.exe -i video.h264 -i audio.aac -vcodec copy -acodec copy -absf aac_adtstoasc output.mp4
>
> Then I found out value of PSNR of output.mp4 referring to video.h264 is only 30.62. It seems a pretty small number.
> Can someone advise how to use ffmpeg to mux H264 and AAC without much quality loss? Thanks a lot!
>

The command you quoted does not encode the video at all, it just
copies it and muxes it to MP4, therefore the PSNR refers to the
original video as well. I don't see how you can get any better quality
than bit-for-bit identical with the source!

Cheers

Tom