[MEncoder-users] DVD to VCD Convertion

[Rich Felker]

On Fri, Jul 22, 2005 at 06:37:14PM -0600, Ron Wills wrote:
> Hello All
> 
>  I've got a quick question. I'm converting a couple of DVD's to VCD for 
> my laptop, which I have been successful doing. I've been able to reduce 

Bad idea. Convert them to mpeg4 video. VCD is very low quality because
of tight constraints and the ancient mpeg1 codec.

> the bitrate for the audio to improve the video quality, but I can't seem 
> to get the stereo channels reduced to mono. I've tried the -lavcopts 
> amode=0 and the -channels 1 options. But when I play back the mpg 
> mplayer says:
> 
> AUDIO: 44100 Hz, 2 ch, 16 bit (0x10), ratio: 16000->176400 (128.0 kbit)
> 
> Checking audio filter chain for 44100Hz/2ch/16bit -> 44100Hz/2ch/16bit...
> AF_pre: af format: 2 bps, 2 ch, 44100 hz, little endian signed int
> AF_pre: 44100Hz 2ch Signed 16-bit (Little-Endian)

MPlayer always considers mpeg audio to be 2-channel, regardless of how
it's actually coded. :) I think it's actually ok.

>  I could be reading the wrong output from mplayer, but everything 
> concerning the audio is saying 2 ch which I'm assuming is 2 channel 
> stereo. Currently the audio channel in the VCD is taking about 120Mb in 
> stereo I should be able just about half this with a single mono channel 
> giving me 640Mb for the video where the quality drop is most apparent.

How much it takes is dependent on the bitrate (i.e. it won't go down
just by choosing mono), and VCD requires a bitrate of 224 kbit/sec
(huge waste). Again, you should ditch VCD. If you're using a lower
bitrate it's not VCD-compliant anyway, so you should just make a much
better file with mpeg4 video and mp3 audio.

>  This is not urgent, but would like to get some insight into this and 
> try to reduce the amount of flicker in the VCDs. Thanks for the help in 
> advance.

My dirty hack to fix it: -lavcopts vi_qfactor=0.1:vi_qoffset=1.5
Again, this won't be a problem if you don't insist on using VCD.

Rich