MPEG2 Hardware Compression or not

[djan]

Hi everybody,

I would like to buy a capture card but I don't know wich technology to use. I already bought a PC TV Card earlier and I had a lot of problem capturing in AVI and all. Losing frames, having audio desynchro and not having the quality I desired. I intend to buy something like Pinnacle PCTV Deluxe wich uses Hardware Compression and has TV Tuner. As I would like to make some DVD's from my captures, I think it's a good solution. What I would like to know is if I lose some advantages not using WDM drivers as the BT878x ? Because with Hardware Compression I can only use the givin program to capture. So, I can't use programs like VirtualDub and all. Maybe I don't need them, I don't know. I'm waiting for your advices. Thx in advance.

[timecop]

depends on what you are going to do.
most <= $200 hardware mpeg cards usually provide marginally useful results. You get a choice of 6-12mbps CBR mpeg2 encoding (of course they cannot do 2-pass in hardware). If you are going to put that on DVD, you'll be limited in how much video you can fit. If you don't want to do any processing on the video other than most basic cutting / splitting, then hardware encoder card is good. But if you want to edit, filter, trim, whatever the video, you might be better off buying a quality capture card using cx2388x chipset to make sure you are getting 10bit/pixel capture, and compress to huffyyuv or something similar, then encode to MPEG2 using some quality VBR encoder.

If you are having trouble doing basic capture and real-time compression to huffy, your system has other problems.

(For example, I remember doing real-time captures on a p2 450, at about 80-95% CPU usage in Win2k, saving the data to firewire hdd)

I'd say keep using your capture card, and use virtualvcr for audio/video sync issue. i had no dropped frames (like 5 per 25 minutes, which was timing related, I think), and no audio desync even on that p2 450).

Anyway, personally I don't think hardware encoding cards are worth it, because you have no control over the encoding parameters.

[djan]

Hi,

First, thx for your answer. I intend to buy a card something like $200. I think it should be a good quality capture card for this price but it has a built-in Tuner and it uses USB2. I don't know its CBR bitrate, I think it's something important to know. Then, I would like to know: isn't it possible to edit MPEG2 source ? As using an AVS script where you can trim, add filters, ... And then use ECC to make out a file with the disered output size. Is it possible ?

[timecop]

Originally posted by djan
Hi,

First, thx for your answer. I intend to buy a card something like $200. I think it should be a good quality capture card for this price but it has a built-in Tuner and it uses USB2. I don't know its CBR bitrate, I think it's something important to know. Then, I would like to know: isn't it possible to edit MPEG2 source ? As using an AVS script where you can trim, add filters, ... And then use ECC to make out a file with the disered output size. Is it possible ?

Of course you can edit captured MPEG2.
You use mpeg2dec3.dll or something similar, Mpeg2Source() etc, do whatever filtering you want on it.

I was under impression you wanted to just take the original encoded mpeg2 and dump it to DVD. Of course if you go avisynth way, you will be recompressing the original MPEG2, filtering/editing it, and encoding it back into whatever format you wanted. If that's what you expect to do, you can probably capture at highest settings the card will allow (like 12mbps CBR or whatever), and then work with that as source material.

If you don't want to re-encode there are plenty of MPEG2 trimming/cutting tools that do GOP-accurate (and some frame-accurate) cutting, but of course you can't edit / filter the actual video.

[djan]

You think a card like Pinnacle PCTV Deluxe at something like $200 can capture at 12Mbps CBR ?

[timecop]

According to http://www.broadcom.com/products/product.php?product_id=BCM7040
The MPEG2 encoding chip used in PCTV Deluxe, BCM7040 is capable of encoding up to 24mbps of MPEG2. Whether that is actually valid for the PCTV Deluxe, I don't know. Pinnacle website seems rather short on details.

[djan]

Ok, I have more details. It can encode until 15Mbps using USB2. Do you think it's a good bitrate to capture and then encode with CCE in VBR ?

EDIT : And finally, is it a better solution to the bt8xx chip ?

[spuddog]

I have a bt8xx card. You might want to try software capture to mpeg2. I use windvr3

[djan]

Originally posted by spuddog
I have a bt8xx card. You might want to try software capture to mpeg2. I use windvr3 Hi,

Even I use a bt8xx card, I would never capture to Mpeg2. First, it's much better to capture to a lossless format. I would use Huffyuv. And then use an encoder to encode the video to any format.

Now, my question is : Is a Mpeg2 hardware capture card better than capturing in Huffyuv with a bt8xx card and then encoding in Mpeg2 ? I would like to know about the advantages of each solution. Thx for your help.

[spuddog]

I don't understand your reply that you would never capture to mpeg2.
you are asking about harware mpeg2 capture, sure there will be some difference between hardware and software caps but there are enough similarities to give you an idea if that's the way you want to go.
as to wether or not mpeg2 or huffy is best it depends on the situation just lok through this forum there are as many ways to do things as there are members. experiment and see what you like.

[djan]

Because compressing to MPEG2 while capturing ask too much processor time. It's not possible to capture with a high bitrate in MPEG2. I think.

[silenceboy]

Can you find SKYNet PHD card in your market?
It can do 15M CBR/VBR MPEG2 capturing.
(Using pillips chip set.)

[timecop]

i'm too lazy to look for the specs on the USB adapter he wants, but according to the specs on the MPEG2 encoding chip, it is supposed to do up to 24mbps CBR/VBR mpeg2, and uses philips saa73xx (or maybe 71xx - whichever is the 10bit a/d one), which would be good if he just wants to capture for editing/re-encoding purposes.

Whether PinnacleTV uses the chip to its full potential or not is unknown, but it shouldn't be too hard to find PDF specs on this.

I guess it all depends. BT878 card will be less quality since you only got 8bit a/d converter, and a old chip.

With hardware mpeg2 compression, there is possibility of artifacts etc on the stream coming from the encoding box. It probably doesn't really matter all that much.

The choice is yours, I guess.

[djan]

I read the PDF file and it's wrote that it can up until 15Mbps. Is it enough ?

[violao]

Originally posted by djan
Now, my question is : Is a Mpeg2 hardware capture card better than capturing in Huffyuv with a bt8xx card and then encoding in Mpeg2 ? I would like to know about the advantages of each solution. Thx for your help.

Hi djan. I looked into PCTV Deluxe for some time and finally gave up. Too expensive to experiment. I read a lot of people had trouble with it on Pinnacle site. Also a lot of finer details from the technical side are hidden, so it's impossible to compare. I think HW encoding is justified only when you are limited in bandwidth (such as USB) or storage (disk).

Personaly I don't believe you may expect a big, shift in quality, if any, moving from bt8x8 to something. bt is capable of capturing full 720x576 without a frame loss. The problems you experience are likely caused by HW & SW in your PC. Desync is caused by separate capturing processes and HW MPEG capture devices sometimes suffer from this problem too. Have you tried VirtualVCR with 'dynamic resample audio' option enabled? For me it delivers perfect sync.

[djan]

In the past time, I was capturing with a Pinnacle PC TV Tuner card based on bt8xx chip. I was using an AMD Thunderbird 1Ghz and only 512MB SDRAM. I was using VirtualDub and I never could capture in 720x576 format. My problem was surely my source and the video deck I was using. I'm sure I can get better results if I use an SVHS unit. My source was really really bad. Something like 5 times worse than normal tape quality and with noisy lines going from up to down. Do you think I may be able to capture this kind of source with a 2Ghz processor and ATA100 HD's and a good SVHS deck ? I think I have my card somewhere in the cellar. I'll try it again soon.

[violao]

Originally posted by djan
...My source was really really bad...
This can lead to frame drops under some circumstances. If you were using compression, (according to my experience) noisy source would put a heavy burden on processor. If your source were OK then 1GHz should probably be sufficient for huffyuv, or even divx. In any case, no capture card will compensate for bad signal. Do everything you can to improve analog signal quality before capturing, like good, short cables, good aerial/tuner/amplifier if needed, use s-video if you can, etc. I am sure bt can deliver wonderful capture if feeded by good signal. And try this VirualVCR. Amazing application and also a freeware. You can even preview full-size while capturing from bt using Smart Tee filter (something you cannot with Virtualdub, due to the constraints of bt card and the fact that Virualdub uses VfW).

[djan]

But in these circumstances of bad source quality, can't a MPEG2 capture card be able to do a good job ? Per example at 15Mbps. It's high, it can maybe even handle the parasite lines going throug the screen. Because with the bt8xx card, the frames with parasite lines where not captured, so I got sometimes 30 seconds of not captured frames. It is too much when you know all the tape is like that.

[violao]

I sincerely doubt that. Perhaps HW codec might do a better job compressing bad signal in real time comparing to SW codec/processor, but you will still get a bad result. And besides, why would you want real-time compression anyway? I think the way to go is to capture uncompressed frames using natively supported codec (such as YV12 for bt), then apply some filtering and finally compress it with high quality encoder using multi-pass VBR. YV12 as opposed to YUV2 might give you less frame drops (12 vs. 16 bits used) and MPEG is YV12 anyway, so it wouldn't matter for later compression. In any case you will improve compression results by filtering out disturbances BEFORE applying comression.

[djan]

Yes you're maybe right, it's what I'll try before to buy anything.