[mythtv-users] mythtranscode and the HD-PVR

Christopher Meredith chmeredith at gmail.com
Thu May 14 03:35:38 UTC 2009


On Wed, May 13, 2009 at 1:48 AM, belcampo <belcampo at zonnet.nl> wrote:
> Christopher Meredith wrote:
>>
>> On Tue, May 12, 2009 at 1:38 PM, belcampo <belcampo at zonnet.nl> wrote:
>>>
>>> Christopher Meredith wrote:
>>>>
>>>> On Tue, May 12, 2009 at 5:10 AM, belcampo <belcampo at zonnet.nl> wrote:
>>>>>
>>>>> Christopher Meredith wrote:
>>>>>>
>>>>>> I know that we don't currently have lossless transcoding of HD-PVR
>>>>>> recordings. But do we have any form of transcoding? I have a script
>>>>>> that converts the MythTV cutlist to an EDL for use with mencoder, but
>>>>>> it is not as precise as I am used to.
>>>
>>> Could you provide this script ?
>>> I would be interested to see if it gives the same results as projectx,
>>> which
>>> has/is the same quality of cutting as mythtranscode, but also unable to
>>> work
>>> with HD-PVR material, only MPEG2 stuff.
>>
>> I actually got it from here:
>>
>> http://www.justlinux.com/forum/showpost.php?p=878967&postcount=4
>>
>> I just had to change the multiplier on lines 39 and 40 to 1001.60000
>> since my recordings have a framerate of 59.940. This script has been
>> working for me, but it is not as precise as I am used to and it does
>> require reencoding (no lossless conversion).
>
> If you would change your HD-PVR settings to a progressive format I think
> things will become a lot easier.
> There have been numerous posts on the mencoder and ffmpeg mailing lists
> about interlaced h264 files.
> Maybe it's worth a test on 1 or 2 files. You then also are able to use
> mencoder's " -oac copy -ovc copy " instructions, so no transcoding.

The HD-PVR is recording in a progressive format. I have my cable box
set to only output 720p and that is the format of all my recordings.

I have been playing a little more with avidemux and Robert McNamara's
h264cut script. I think I finally have everything working just right
so that I can get lossless transcoding of HD-PVR recordings that use
the MythTV cutlist and is accessible from mythfrontend and mythweb.
The cuts aren't frame-precise, but they are very close.

Right now, my HD-PVR is recording HD content at about 3500 kbps, which
is about what I would use for x264 transcoding before, when I was
grabbing MPEG2-TS off the cable box with firewire. Now, rather than
having to record the program, use mythtranscode to excise the
commercials, then hand the file over to Handbrake to process for about
18 hours, I can have a finished MKV with h.264/AC3 about 20 minutes
after the recording finishes. Loving it!

On suggestion for Robert, if you're reading this. I know you said your
mythcommflag patch is an ugly hack. It may well be. But mythcommflag
already has an option to simply output the cutlist. Rather than
patching mythcommflag to create an avidemux project file, would it be
possible to write a script that generates the project file from the
cutlist as outputted by mythcommflag with the --getcutlist flag? That
would make it much easier to upgrade trunk without having to repatch.


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