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Best framerates/resolutions/formats for S-Video sampling?
PostPosted: Fri Mar 30, 2007 7:21 am Reply with quote
Joined: 23 Mar 2007
Posts: 13

I would like to use the S-Video input on my pcHDTV 5500 to digitize some old Hi8 camcorder tapes.

I have a couple of "newbie" questions...

1. What is the best resolution (X x Y), framerate (fps), and/or bitrate (bps) for transcoding S-Video signals on this hardware?

(I want to preserve as much of the native resolution as possible so I don't want to undersample; on the other hand I don't want to eat up unnecessary diskspace or overly task my hardware so there is no point in oversampling beyond what exists in the analog S-video signal. Also, is there a "native" resolution/framerate/bitrate that works best with the pcHDTV hardware)

2. What is the best format for initially sampling to?
Although ultimately, I want to convert to xvid/MP4, I am not sure that my hardware can support high quality real-time transcoding (P4- 2.8Ghz)
So I am looking for an intermediate format that has some compression but with minimal loss that is both fast and good as an intermediate format before converting to MP4.
(I am assuming that just mindlessly recording 'raw' data would take up too much diskspace and that there is some intermediate low loss, fast compression format that would make sense instead)

3. Is 'transcode' the 'best' readily available/free program for first capturing (and then later transcoding) the combined audio and video stream? It seems to allow for a flexible combination of codecs and formats.

4. Is there any advantage in routing the (separate) audio signal first through the pcHDTV card and then back out through my soundcard or is it better just to route the audio signal directly from the audio output of my camcorder to my soundcard?
(my understanding is that when using S-video, there is no A/D converter available for audio on the pcHDTV 5500 card so the audio signal ultimately needs to be digitized by my soundcard anyway)
I am looking for the solution that gives the best quality and A/V synchronization.

5. Finally, I also have the possibility to input S-Video through an old Winfast 2000XP Deluxe card or (using rivatv) through my nVidia GeForce Ti 4600 ViVo graphics card. But I am assuming that the 'newer' pcHDTV will likely work better since we know that it is "newer" technology (the other cards are ~4 years old) and is built to handle the even higher bandwidths required by HD. Is this right or would I be better off using the other cards or even perhaps a dedictated other sampling card?

In summary, my key requirement is to get as good a quality digitization of my old analog Hi8 tapes. Speed and diskspace are only secondary concerns.

I hope these questions make sense and are not too naive...

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Re: Best framerates/resolutions/formats for S-Video sampling
PostPosted: Fri Mar 30, 2007 9:06 am Reply with quote
Joined: 06 Jul 2006
Posts: 125

Resolution = 720 x 480, framerate = 60 interlaced fields per second.

Encoding: Probably RTJPeg, set the bit rate according to required quality.

There is no advantage to using the sound in port on the card; it will simply be electrically connected to the patch cable to your sound card, so you may as well just hook it up to the sound card directly.

There is also probably no advantage to the pcHDTV for analog sampling over your other cards, and may be some disadvantage, in that the cx2388x isn't considered by many to be the best card for analog, though some of that may have been due to problems with the drivers.
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PostPosted: Fri Mar 30, 2007 9:33 am Reply with quote
Joined: 23 Mar 2007
Posts: 13

This is really helpful! -- couple of follow-up.

1. First, I just wanted to clarify that you are suggesting recording in native NTSC *interlaced* format. Then in the second transcoding step to mp4, I would do the deinterlacing. Right?

2. Is there any practical difference between 60 interlaced fps and the 29.97 NTSC rate (is that the non-interlaced rate?)

3. Is RTJPeg available as part of 'transcode' or is it something unique to mythtv? (and I am better off using the configurability and directness of the raw 'transcode' program or should I just use something like mythtv to record the signal)

4. While the cx88 may not be a perfect chip, am I right in assuming that it is at least *better* than the bt878 chip in my Winfast 2000XP or the Philips saa7108e chip in my nVIdia ViVo card?
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PostPosted: Fri Mar 30, 2007 2:36 pm Reply with quote
Joined: 06 Jul 2006
Posts: 125

Yes, record in interlaced format and do the de-interlacing during transcoding. That way you can use a deinterlace filter which is compute intensive.

The NTSC frame rate is that 29.97, the field rate is 59.94. I'm not familiar enough with 'transcode' to tell you what to tell it.

"Transcode" can't handle making RTJPEG on the way in (though it can decode it), unfortunately. So you have to either use MythTV to record or pick another codec; I don't know which is best of those transcode does support.

The cx88 should be better than the bt878, but I have no idea relative to the saa7108. For what it's worth, I never noticed any difference between the cx88 and the saa7134 (which has a better reputation).
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Best framerates/resolutions/formats for S-Video sampling?
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