[mythtv-users] Commercial Flagging vs. Transcoding

J. Donavan Stanley jdonavan at jdonavan.net
Wed Feb 18 17:04:30 EST 2004


John DeLuca wrote:

> I currently transcode all recordings (set to kick off immediately 
> following completion of recording).  I don't intend to save the 
> files...I merely transcode to have the commercials flagged so when I 
> watch them later, I can skip past them (assuming it's done a good job 
> of properly detecting commercials).
>  
> In reading another post, I am wondering if I really need transcoding?  
> I have a PVR-x50 and the recording profiles are set up for MPEG2- at 
> 2200 bits for 720x480.  That's also the setting of transcoding.  My 
> questions are:

Bit rates are bit rates.  To benefit from transcoding you want to lower 
the bit rate.  MPEG4 can produce better looking images at lower 
bitrates.  2200 is REALLY low for the resolution you're capturing your 
MPEG2 stream at.  Try 440x480 at that bitrate and you'll notice a nice 
improvement in image quality for "free" (assuming you're capturing NTSC)


>  1. Do I benefit from transcoding other than for commercial 
> detection?  I assume there's perhaps some space saving since Iguess I 
> go from MPEG2 to MPEG4 in the transcoding process.


Commercial flagging and commflagging are two different things.  
Commflagging happens before transcoding does.

> 2. If there's little/no benefit to transcoding (if I don't plan on 
> saving the recordings after I watch them), should I just use the  
> mythcommflag before going to bed or on a schedule if that's the only 
> real goal?

If you're not keeping the recordings around there's no point in 
transcoding.  Just set "Automaticly flag commercials" and leave it at 
that.  You shouldn't ever need to run mythcommflag by hand under normal 
circumstances.



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