[mythtv-users] Transcoding, mpeg-2, mpeg-4 ASP vs. AVC

[Phill Edwards]

> I'm getting a little bit confused as to what MythTV is doing on the
> transcoding front.
>
> I'm recording UK SD DVB-T mpeg2 streams. I'm struggling to keep up with the
> stuff I'm recording, so I'd like to transcode where possible.
>
> I've got the system transcoding files, I know it is using the "From MPEG2"
> profile. (When I change the bitrate the transcoded filesize changes.)
>
> I understood mpeg-4 ASP to require approx. half the bitrate / filesize that
> mpeg-2 does for an equivalent quality file. Then mpeg-4 AVC is even better,
> requiring perhaps a third what mpeg-2 does.
>
> I tried adjusting the settings, but I'm seeing a significant drop in the
> quality, even with a modest reduction in bitrate.

I'm recording with DVB-T cards (therefore MPEG2) and transcode to
MPEG4 with great results.

My transcode settings are:
Video - Bitrate:2500, Max Quality:2, Min Quality:15, Max Quality diff
bt frames:3, none of the other checkboxes ticked.
Sound - MP3, Samplg Rate:32000, MP3 Quality:5.

I think this is reducing the files to about 60% of the MPEG2 size.

Regards,
Phill