[mythtv-users] How to record HD and SD versions of same show

[John Sturgeon]

David Shay wrote:

>----- Original Message ----- 
>From: "Brad Templeton" <brad+myth at templetons.com>
>
>  
>
>=> Or you could write a script to transcode/down-rez the HD version and
>  
>
>>keep it in videos.   It will look much better than any version recorded
>>off something like a pvr-250, and may look better than a version recorded
>>off the SDTV digital subchannel, if that's what you are doing.
>>    
>>
>
>I am recording the SD versions on a pvr-250.
>
>Well, I've tried various ways to transcode/downres the shows from the HD
>channels and I can get that working well enough for actual Mythfrontends.
>My problem is that I am also using some Hauppauge MediaMVP psuedo-frontends
>and I can't seem to get a working mencoder or other command to transcode
>down and play correctly, i.e. with correct A/V sync and the ability to skip
>forward/backward correctly.  Yeah, that's really an issue for the MVP list,
>but that's why it's not a real suitable solution at the moment.  Anyone care
>to share there favorite command lines to downres HDTV content?
>  
>

David,

You can use projectX to demux the video and audio then use transcode on 
the video, then avimerge to remux them:

my transcode parameters are as follows (two pass for best quality lowest 
file size)

transcode --nice +10 -y ffmpeg -F mpeg4 -Z 640x,fast ***

*** optionally, --export_asr [23] (2=4:3 3=16:9)  -w nnnn (bitrate) -R 
[123] (multi-pass, single pass, etc) -I [34] (deinterlacing)

Here is what I would do for 1920x1080i

1) use projectx to demux and fix out of order packets (resulting in 
*.mpv *.ac3)
2) use transcode to transcode the video down
first pass:
transcode --nice +10 -y ffmpeg -F mpeg4 -Z 640x,fast -I 4 --export_asr 3 
-R 1 -w 2000 -i filename.mpv -o /dev/null
second pass:
transcode --nice +10 -y ffmpeg -F mpeg4 -Z 640x,fast -I 4 --export_asr 3 
-R 2 -w 2000 -i filename.mpv -o outputfile.nosound.avi
3) use avimerge to multiplex the ac3 back into the avi
avimerge -i filename.ac3 outputfile.nosound.avi -o outputfile.avi

Then I move the file over to my videos directory for MythVideo to 
playback (using mplayer).

Ways to speed up the transcoding process:
1) don't deinterlace (delinterlace on playback using mplayer -vf pp=lb)
2) do single pass, and bump the bitrate up
3) don't resize (if disk space is the issue, you can just re-encode to 
MPEG4 HD at about 5k bitrate.)

-- 
John Sturgeon <><
http://www.sturgeonfamily.com/mythtv.php