[mythtv-users] HD MPEG-2 to MPEG-4 transcoding

[Joel Turner]

brad+myth at templetons.com wrote:

>On Sun, Jul 16, 2006 at 11:18:59PM -0700, Yeechang Lee wrote:
>  
>
>>My 3.0GHz Pentium 4 frontend/backend took 458 minutes to transcode,
>>without resizing and at a 5000Mbps bitrate, a 15.7GB 125-minute HDNet
>>(18000Mbps) Movies recording to a 5.7GB MPEG-4, a 3.67:1 time ratio
>>and a 64% space savings. (Both mythbackend and mytfrontend were active
>>at various times during the process.) I'd love to see mythtranscode be
>>able to use x264 for the better video quality at the same bitrate
>>(since User Jobs remains a mystery to me), but suspect that encoding
>>times would, as you note, become even more painful.
>>    
>>
>
>Most people who have tried to transocde HDTV mp2 recordings to mp4
>have reported annoying audio sync problems after doing this.   This
>is with mencoder which is used by myth's transcoder.
>
>If you're getting it with perfect audio sync, I would be interested
>to see your various flags and options to experiment with them.
>
>My own transcodes have tended to be no-resize for 720p, and
>resizing to either 1280x720p (with deinterlace) for 1080i, or
>1280x540p (easy deinterlace here) because my tv is 1280x720 like
>most TVs of the past couple of years.  (1080 line TVs are now
>becoming more common.)
>
>I haven't yet tried but might want to experiment with 1280x1080i,
>with no deinterlace, but still throwing away the extra horizontal res
>I can't see on my TV.
>
>At any rate, I have found that when going to 1280x540, which is 75% of
>the pixels on my TV, I can get quite decent visual transcodes in 1.5 gb
>per hour, which is a nice compact data rate.   Even less than
>your 2.76 gb/hour.
>
>However, the audio has rarely been satisfactory.
>
>My transcode times are not nearly as bad as yours though.
>Don't forget to add the turbo option to the first pass if doing a 2-pass.
>Frankly, the 1 pass transcodes aren't that bad.
>  
>
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>  
>
I tried mythtranscode and found the results satisfactory for MPEG-4. I 
admit that I haven't spent much time tweaking command line flags. I 
already have established workflows for xvid conversions on my XP box 
that produce great results.   What started all of this was a recoding I 
made several weeks ago of Bugs Life on ABC.  According to Apple 
literature, DVD Studio Pro will allow you to author HD source onto SD 
media (complete with 16:9 menus) using the H.264 Codec. I have yet to be 
succesful in actually doing this and was put off by the 1.2 hour time 
that Compessor reported that it would take. I have some other PC's 
available to me that I might try and see if I can bring the encoding 
times to a more reasonable level say 20 FPS.  IfAt 1.78FPS, this is just 
not worth the effort.

Apple's implementation is not entirely compliant but my int