[MEncoder-users] DVD to VCD Convertion

[Ron Wills]

Rich Felker wrote:

>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.
>
>  
>
  Definitely makes sense... As for my laptop, it has only been able to 
handle the VCD's. Old Toshiba with a bugging video card (trying to use 
any accel in Linux locks the monitor, grrrr, only works with vesa). So 
any kind of quality, on that machine, and no hw accel, it's like 
watching a slide show rather than a movie :P.
  Just out of curiosity, if I encode it to mpeg4, the video would only 
be able to played on a computer? As I understand it DVD players only 
play up to mpeg2 video with ac3 audio (not sure about other audio 
encodings). This is what I seem to recall from my DVD specs.
  I know this may seem like an absolute waste of time, but what better 
way to learn than by getting your feel wet ;)

>> 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
>
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>