I am about to purchase the AverMedia DarkCrystal HD Capture SDK C727 Card from Amazon which has HDMI input.
I want to capure video in 1920 x 1080i from Sky HD satellite set top box.
Will Dr HDMI on its own allow me to do this? Has anyone here successfully managed to do this with Dr HDMI ?
Many thanks for any advice,
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Thread: Dr HDMI Question
AFAIK The $ky Box has only one hdmi output. So if you want to watch on your tv while you capture, or even just not to keep switching cables, you need a hdmi-splitter.
Some of these splitters act as unofficial (since it is technically illegal to bypass the copy protection) HDCP stripper and some do not. Even those that look like ones reported that work may not.
Try without a splitter/stripper first but if you get a blank screen you then know.
Thank you for your replies,
Yes, there is only one HDMI socket on the sky box. So, I would need a splitter.
Does anyone know of a spiltter that would work in this situation? So, that I would not Dr HDMI? Is the PQ compromised? Can you please send a link.
You seem to have got lucky there.
Note that this ships from that well known actress Kally Fornia so will take a few more days to arrive.
Can you please tell me if the AverMedia DarkCrystal HD Capture SDK C727 Card can capture video from HDMI in the original raw uncompressed format? Without any re encoding? Someone told me that all HDMI capture cards re encode when capturing?
You had better read:
They write about 'uncompressed' capture and then mention mpeg-2 and h.264 in the capture spec.
I read that but I am none the wiser. It does not say whether it compresses all captured video or whether it is untouched...
What do you think?
I do not think but I might guess.
'Uncompressed' in its strictest sense means 2 gig per second (it is late so excuse if I got the math wrong). The card has analogue inputs so it may well be able to capture analogue video 'uncompressed'.
The signal over hdmi is already compressed. The video could be encoded mpeg-2 or h.264. I do not know what $ky uses. If was to guess then I would say mpeg-2.
The card might well capture that 'as is'. So it does not re-compress. It is still high bitrate and your system, expecially the HDD, will need to be fast enough to grab it. But it is not 'uncompressed'.
Well you will find more users of Black Magic products on here so do search the forum.
BTW on that Amazon page you linked to you will see various other hdmi splitters so if were thinking of getting one of those..........
There might be a driver or software crack that works with that card that will allow it to capture HDCP protected content without using an HDCP stripper. Worth a try:
1920x1080 YUY2 at 30 frames per second is about 125 MB/s (~1 Gb/s. You'll probably be capturing at 25 fps so your bandwidth requirement will be 20 percent lower). You'll need a raid array to capture that uncompressed. A fast lossless codec like huffyuv or ut video codec will get the bandwidth low enough for a single desktop hard drive. You'll want to capture to an internal SATA drive that's not your boot drive.
The Black Magic cards are very picky about what they will capture and what computers they will run on. I don't recommend them.
Last edited by jagabo; 29th Apr 2014 at 18:19.
OK, many thanks. I am tired, and can no longer take any more information in..
It seems like the aver media is better than the black magic. I believe all capture cards re compress. So, I will just have to get one and try it out.
Last edited by usually_quiet; 29th Apr 2014 at 19:05.
Thanks usually_quiet - Would you say it is better to get a card with hardware compression as opposed to software? I thought the Avermedia C727 had hardware compression.
Also, is it possible with the Avermedia C727 card to store the captured data uncompressed? I dont want to re-compress if I can avoid it. Until now, I was capturing the raw .TS files in a set top box and the H264 capture file was untouched, which was great. But, I can no longer to do this, and have been forced to go down the pci card route. I wanted to continue capturing and storing raw files, as I did in the past.
Is this possible?
You cannot capture the broadcast TS stream with the Avermedia. The satellite box decompresses the TS stream and sends uncompressed (HDCP encrypted) video over the HDMI cable. That uncompressed video is around 400 GB per hour. You'll need a RAID array to handle that comfortably.
If you use a lossless codec the file size will be reduced to about 1/3 that amount -- which can be written to a desktop hard drive. Or you can use lossy software encoders like MPEG 2 or h.264. That will get the size down to 5 to 20 GB/hr depending on what bitrate you choose. But with software encoding you'll need a fast CPU and you probably won't want to use your computer otherwise while capturing (or you risk dropping frames). Realtime software encoders don't deliver the best quality. They have to take shortcuts in order to work quickly.
If you use a hardware encoding capture device the video is compressed before it gets to the computer (much like the broadcast TS stream), typically to about 3 to 6 GB/hr. It's possible to write that data directly to a file with hardly any CPU usage at all (you can continue to use the computer while capturing). If you view the video while capturing you usually see about 5 to 20 percent CPU usage (depending on your CPU, graphics card, etc.). Realtime hardware h.264 encoders aren't great either. But I think they're better than realtime software h.264 encoders.
So, with software encoding devices you have the option of capturing exactly what comes over the HDMI cable, byte for byte, with no quality loss. But computer hardware requirements are high. With hardware encoding devices you always lose some quality because the video is always re-compressed with a lossy codec. But computer hardware requirements are low.
Basically, if you just want to capture and archive (maybe minimal editing like cutting out commercials) a hardware encoder is ok. If you plan on editing, filtering, and want the highest quality, a device that allows uncompressed or losslessly compressed capture can give you better results. But computer hardware requirements are high and you will be spending a lot of time working on the video.
To add to jagabo's post above, here are figures I took from from Wikipedia estimating the file sizes you would have if you captured uncompressed video.
625 PAL uncompressed
8 bit @ 720 x 576 @ 25fps = 20 MB per/sec, or 70 GB per/hr.
10 bit @ 720 x 576 @ 25fps = 26 MB per/sec, or 93 GB per/hr.
720p HDTV uncompressed
8 bit @ 1280 x 720 @ 59.94fps = 105 MB per/sec, or 370 GB per/hr.
10 bit @ 1280 x 720 @ 59.94fps = 140 MB per/sec, or 494 GB per/hr.
1080i HDTV uncompressed
8 bit @ 1920 x 1080 @ 25fps = 99 MB per/sec, or 348 GB per/hr.
10 bit @ 1920 x 1080 @ 25fps = 132 MB per/sec, or 463 GB per/hr.
Thanks to you both for that very useful information. I was not aware that so much was involved...
So, the last few years I have been capturing HD broadcasts on my dreambox and recording the original .ts file onto the internal HDD inside the dreambox. And watching it later and archiving.
By doing this, was the signal re-compressed somewhere? If so, where and how? What do I need to do maintain the PQ I had using this method with a HDMI capture card? Is it even possible?
As I said earlier, and now you mention a dreambox it is somewhat clearer......
A dreambox records the original stream. It does not compress. It does not re-compress. But the original stream is NOT uncompressed. H264 video is compressed.
Now I might have confused you earlier (I might have confused myself as well). Your stream is compressed as it arrives in your $ky box. Over hdmi to your tv the box will convert it to a format that the tv understands. That may well be your notion of 'uncompressed'. Your proposed capture device would also accept that 'RAW' stream and thus not re-compress it. And it has been pointed out that uncompressed means HUGE file sizes and a pretty hefty PC as well.
I think you are getting paranoid about compression due to your misunderstanding of what was stored in the dreambox. Like I said, it was compressed. Your new card can compress back to that original H264. The real issue is whether a software encoder is better in real time than a hardware one. For real time compression, especially for high bitrates and HD, hardware compression wins hands down.
But you do have an alternative to PC recording. $ky+HD
So, when I recorded the HD broadcasts in .ts on my dreambox - the file was already compressed? In media info - the ts file is H264 with 13 Mbs bitrate - and the filesizes were approx 5 GB for a 1 hour broadcast.
I dont think the dreambox was encoding or compressing - as you say, the broadcast signal was already compressed into H264.
So, what do I need to do, to accomplish the same with a capture card? Can I just capture the already compressed signal and not encode/compress again? Would the resulting filesize be the same as the dreambox ts files?
I am very sorry for all these noob questions.
The beauty of a dreambox is that it transferred its recordings over a LAN to your PC EXACTLY as it stored them. I know of no other PVR that can do that.
So you have to use other cables and standard capture techniques. You have two choices:
1. Capture as uncompressed >> HUGE file size and re-compress that in software on the PC. Since that re-compression is not in real time you can use the encoder more effectively.
2. Capture as compressed.
Would the file sizes be the same ? Possibly with hardware compression in method 2 or good use of x264 settings in method one but since all broadcasts are different it's a tough call.
But, why would the PCI card capture the signal as uncompressed if the broadcaster has already compressed it? I am confused,
You got the last bit right.
The broadcaster sends a compressed signal. Your receiver converts that. Your card receives that converted signal and passes it to your PC either 'as is' or re-compresses it.
Ohh okay. And so, when I was recording the ts broadcasts on the dreambox - what was happening in there? The dreambox converted the compressed signal that it receives and then what? How was the .ts recorded? Before the box converted after or after converting?
Last edited by jagabo; 30th Apr 2014 at 09:55.