[mythtv-users] Optimum encoding for remote mythtv
mythtv at skunkeye.com
Wed May 12 22:30:52 EDT 2004
> Those settings are currently 720x480 with a max bitrate of 3000 and audio
> at 48000 and 96k. There is only an analog cable input to the PVR-250, so I
> am sure those settings are overkill and are making the files larger than
> they need to be for the quality I would find acceptable.
> My question is can someone suggest better settings? Obviously, I can test a
> variety of encoding settings but it's not so painless because I then have
> to download the file before visually inspecting it.
> Currently, my idea is to drop the resolution to NTSC level (approx 352x525)
> while leaving the max bitrate at 3000. Am I heading in the right direction
> with this change?
You're halfway there. Bitrate is bitrate, so the files will likely be
pretty much the same size, since you're allocating the same number of
bits (per second) to the stream.
I would start with reducing the size, and reducing the bitrate by a
comparable amount. The smaller frame size will probably make the TV
picture a bit less sharp, but will allow you to lower the bitrate (since
you have less pixels per frame), which is where the file size decrease
will come from.
I would probably try cutting the frame size in half (352x480), and
reducing the bitrate to 2200 or so. Test that out on a short recording,
and adjust from there.
You might not be able to get very much smaller files (at least with
acceptable quality) out of the PVR-250, since MPEG2 is kind of notorious
for producing large files, and for producing poor quality at extremely
low bitrates. Your next step might be to auto-transcode everything to
MPEG4, which will produce a significant reduction in size (without much
quality loss), at the expense of having to wait for it to transcode. A
2.4 GHz processor with a PVR-250 is probably 90% idle all the time
anyway, so put the CPU to work.
You might also cut the audio sampling to 44100 (or even 32000); it won't
gain you much, but at 96kb/s, you won't be able to hear the difference
More information about the mythtv-users