[FFmpeg-user] optimized bitrate

[Hugo Wau]

Thanks Carl Eugen and Bob,

On 24.09.2012 18:19, Bob Maple wrote:
> On 9/24/2012 6:05 AM, Hugo Wau wrote:
>
>> Now I would like to have a (Linux) bash script, where the right bitrate
>> is calculated from the length of the audio or from the number of the
>> single images, from which the video is made.
>
> You can calculate a general bitrate by taking the maximum number of 
> bits you are able to store, and divide by the number of seconds of 
> material you have.
>
> So say you had a storage medium that could hold 100000 bits and had 62 
> seconds of material to store on it, your data rate couldn't exceed 
> about 16kbits/sec.
>
> Don't forget to include your audio in the estimate, and some pad for 
> overhead (DVD IFO files, etc.)  Then rather than trying to guess and 
> use a q-factor, compress to the desired bitrate.
I noticed some audio distortion right after starting the video or 
directly after jumping to a certain place, using VLC-player for playback 
in those videos, to which I had applied the "-b 5000k" option. This 
distortion did not appear in those videos to which I had applied the 
"-qcomp" option. Now I think, that i have to play around with the -vb 
option if this only applies to the video-bitrate, since I do not want 
the audio quality to be reduced or affected in any way at all.

I still do not understand why the -b option needs to be placed right 
behind the ffmpeg command, while the -qcomp option only works if 
l´placed close to the end of the command (behind the video codec). Where 
does the -vb option need to be placed?

With kind regards
Hugo