[mythtv-users] down sizing

[Michael T. Dean]

On 01/10/2014 02:23 PM, Daryl McDonald wrote:
> But can you trancode a 14+GB recording small enough to fit on a 4.7GB DVD?

The important part is how long the recording is***.  If it's a 14GB, 
2-hr recording, you can transcode it to a DVD-compliant stream that will 
fit on a DVD.  If it's a 14GB, 14-hr recording, you can't transcode it 
to a DVD-compliant stream /of useful quality/ that will fit on a single DVD.

Note that size is dependent on bitrate and length of the video--where 
bitrate is basically an indicator of the quality of the video.  So, if 
you need extremely low bitrate over a long time to get the video small 
enough to fit, you'll have low quality.  If, instead, it's rather 
short--1 to 2 hrs of video--you should be able to get "up to DVD 
quality" video to fit on the DVD.  And, as you may guess from this 
paragraph, taking a 7GB/hr video and transcoding it down to a 2GB/hr 
video that fits on a DVD will mean a reduction in quality.

Note, too, that if you're not trying to make a DVD-compliant DVD, but 
instead just trying to stuff data on a DVD data disc (i.e. a video file 
on a disc), you have more options in that you can choose to use a 
more-efficient CODEC, such as H.264, rather than being constrained to 
MPEG-2, as required by the DVD spec.

Mike

*** And, to a lesser extent, the type of imagery in the video.  
Real-world images require much higher bitrates to get useful quality 
than would, for example, animated shows.