[mythtv-users] HD MPEG2 ->SD DVD?

[Nick Rout]

On Mon, Jul 14, 2008 at 3:26 PM, George Mari
<george_mythusers at mari1938.org> wrote:
> Ma Begaj wrote:
>> 2008/7/14 George Mari <george_mythusers at mari1938.org>:
>
> [deleted]
>
>>
>> It would be great to be able to downscale video on the fly when a user
>> wants to play HD recording or an HD Apple trailer in MythVideo with
>> mplayer.
>>
>> Does downscaling video need more power than watching it? Probably
>> little bit more and I mencoder or some other tool could do it. It
>> could write the output in a new file, and mplayer on the
>> notebook-frontend would read from it. I did not try this, but it could
>> maybe be done for mplayer/mythvideo:
>> 1. user runs a scripts which should start the video playing
>> 2. the scripts connects over ssh to the powerful backend and starts
>> downscaling the video and saving it in a new file
>> 3. a few seconds later mplayer (on the frontend) starts with reading
>> from the new file
>>
>> fast forward is probably not possible.
>>
>> what do you think about this idea?
>
> The slow part is not the scaling, it's the decoding of the MPEG2 file in
> a time fast enough to get each frame onto the screen, before the next
> one needs to be displayed.
>
> Lower bitrate HD recordings are easier for slower systems to display
> than ones with higher bitrates, just because there is less data to
> decode.  Of course the trade-off is a lower quality picture, in general.
>
> In order to scale the video, it first has to be decoded, so the
> slow/hard part has to happen first before the easier part (scaling) can
> be done.
>
> On-the-fly transcoding down to a lower bitrate and/or resolution would
> be nice, but not generally doable, I think.  There may be something
> similar going on with some of the streaming options that I believe
> MythWeb has, but I'm not certain on this.
>
>

VLC is a common way of people doing on the fly transcoding, but as you
say it will require a lot of grunt on the backend.

However a big barrier in this instance will be 802.11. Try a wired LAN
and see what results you get before blaming it all on the CPU. :-)