Originally Posted by
coldraven
if I want medium quality mono sound where do I alter the argument?
As an output option (anywhere after "-i input" and before "output.foo") you can add "-ac 1". If you apply as an input option you are telling the decoder that the input is i channel, even if it is stereo, which probably isn't something you want to do (or maybe ffmpeg will ignore it).
Vorbis CBR:
Code:
ffmpeg -i input -c:v libvorbis -ac 1 -b:a 32k -c:v libvpx ... output.webm
Vorbis VBR:
Code:
ffmpeg -i input -c:v libvorbis -ac 1 -q:a 3 -c:v libvpx ... output.webm
See Recommended Vorbis Encoder Settings for an idea of what "-q:a" value to use.
I'd like to figure out how to use libvpx and then write a proper FFmpeg guide for it (and HTML5 video with ffmpeg)... but hopefully someone will beat me to it.
See the FFmpeg and AAC Encoding Guide for full details and examples for AAC encoding, and FFmpeg and AAC Encoding Guide for encoding to H.264 video.
Originally Posted by
coldraven
I'm presuming that it is better to capture directly into the format I want rather than transcoding afterwards.
The main example in this guide attempts to capture as fast as possible without having to work on compressing things very much so you can achieve your desired framerate (assuming your CPU is the bottleneck). It then suggests re-encoding this temporary, large, lossless output to your desired final output(s). This may also be the best choice for you if you're going to make a mp4 and webm from the same source.
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