[FFmpeg-user] Converting video + stereo to video + mono

[Carl Eugen Hoyos]

Jason Heeris <jason.heeris <at> gmail.com> writes:

> I'm playing around with encoding video for HTML5, and I 
> was wondering if converting the stereo audio to mono would 
> have any real effect on size.

Only -ab (or -aq) has a real effect on size, I am not sure if 
you can improve quality (but it should for real stereo input).

> So I tried using the "-ac 1" option in this invocation:
> 
>     ffmpeg -i Input.avi -vcodec libx264 -b:v 1000k -ac 1 Output.mp4
> 
> ...but the resulting output still seems to have stereo audio.

Why do you think so?
Your console output reads:
Output #0, mp4, to 'Output.mp4':

[...]

    Stream #0:1: Audio: aac (@[0][0][0] / 0x0040), 44100 Hz, 
1 channels, flt, 128 kb/s

Carl Eugen