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

John Sturgeon mythtv at sturgeonfamily.com
Wed Apr 20 14:16:10 UTC 2005



john roberts wrote:

>I 2nd the request.
>
>I haven't had much luck in down-res'ing my HD shows.
>
>-John
>
>----- Original Message -----
>From: "David Shay" <david at shay.net>
>To: "Discussion about mythtv" <mythtv-users at mythtv.org>
>Subject: Re: [mythtv-users] How to record HD and SD versions of sameshow
>Date: Tue, 19 Apr 2005 15:17:58 -0500
>
>  
>
>>
>>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?
>>
>>    
>>

Sorry it took me so long to get the message out.  I responded from the 
wrong e-mail address and it got stuck.

David and John,

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





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