Any of the PCI cards support downconversion? - AVS Forum
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Old 07-02-2001, 12:56 AM - Thread Starter
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Obviously, one of the big problems with HD recording is the disk space involved.. The data streams at 1080i or 720p are huge.

I would be very interested in a device with the capability to convert a high-res stream down to something around 480p. This would allow us to keep the widescreen format, at a decent (user selectable?) resolution. And, it would allow us to store A LOT more shows than at full res..


But, doing this changes the process from recording the raw MPEG2 stream to (I assume) decoding it, downsampling it, and re-encoding then saving..

Is this realistic for today's hardware?
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Old 07-02-2001, 09:56 AM
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None of the cards will save a downconverted stream but the data from the HiPix and WinTV-HD cards can be converted in a batch job.

There have been good results converting them to HD/4 960x540p, taking less than 1/3 of the disk space with little loss of quality. Search the HTPC forum for a title like "HD playback in Software Only". (approx)

- Tom

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Old 07-02-2001, 09:58 AM
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Two of the current HD cards can downconvert to 480i or maybe 480p (I'm not quite sure which format), but you would have to capture this data using a low compression codec on all but the fastest machines. Currently, the software for these cards does not support the capture of the downconverted HDTV signal, but is should be possible.

In any event, real time storage and encoding of standard def TV pushes most current PCs right to their performance limits. PCI bus traffic being one of the primary areas that causes dropped frames if you have a fast enough CPU to compress in real time.

Just to explain the technology involved a little more if your interested, the software used by the HD card uses directshow filters there are ways to insert a filter into the render pipeline that will attempt this, but since the application software builds the filter graph internally, it would take a little bit of hacking to get it to work.

Ah, Tom beat me to the punch, and that is a nice and easy way to convert the files. I think Tom is using the Elecard decoder and maybe a MPEG-4 encoder such as Divx. But as Tom says, you first have to record the HDTV stream and then convert it to something else. That takes quite a lot of CPU time so this in not a real time solution.


[This message has been edited by JoeFloyd (edited 07-02-2001).]
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Old 07-02-2001, 10:13 PM
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Hmmm. A little bit of a crossed post above.

I actually haven't been doing the above yet, I was just quoting answers I've gotten from asking similar questions. I probably won't be converting anything until the HD/4 version of the Elecard software is available, or until I run out of disk space.

My own intention was to store these either on DAT or DVD-R, whichever gets cost effective first. I think the data rate involved would allow playback from either of these in the HD/4 format.

- Tom

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