Login | Register For Free | Help
Search for: (Advanced)

Mailing List Archive: MythTV: Users

HDMI capture card with linux drivers

 

 

MythTV users RSS feed   Index | Next | Previous | View Threaded


joel.donahueis at gmail

Apr 15, 2010, 8:43 AM

Post #1 of 22 (10385 views)
Permalink
HDMI capture card with linux drivers

http://www.blackmagic-design.com/products/intensity/


"Intensity Pro is the world’s first HDMI and analog component, NTSC/PAL and
s-video PCIe capture and playback card for Windows, Mac OS X and Linux
computers."


Not sure what it would take to get this to work with Mythtv. Would need to
get a HDCP stripper for the signal but from what I can tell it should be
possible. $199 is fairly reasonable.


beww at beww

Apr 15, 2010, 8:52 AM

Post #2 of 22 (9346 views)
Permalink
Re: HDMI capture card with linux drivers [In reply to]

On Thursday 15 April 2010 09:43:47 am Joel Donahue wrote:
> http://www.blackmagic-design.com/products/intensity/
>
>
> "Intensity Pro is the world’s first HDMI and analog component, NTSC/PAL and
> s-video PCIe capture and playback card for Windows, Mac OS X and Linux
> computers."
>
>
> Not sure what it would take to get this to work with Mythtv. Would need to
> get a HDCP stripper for the signal but from what I can tell it should be
> possible. $199 is fairly reasonable.
>

The first thing you would need would be a LOT of storage. I think this device
creates uncompressed video, difficult to deal with in a Myth type system.
Compressing it on the fly in software would require a LOT of computing grunt.

_______________________________________________
mythtv-users mailing list
mythtv-users [at] mythtv
http://mythtv.org/cgi-bin/mailman/listinfo/mythtv-users


raymond at wagnerrp

Apr 15, 2010, 9:04 AM

Post #3 of 22 (9207 views)
Permalink
Re: HDMI capture card with linux drivers [In reply to]

On 4/15/2010 11:43, Joel Donahue wrote:
> Not sure what it would take to get this to work with Mythtv. Would
> need to get a HDCP stripper for the signal but from what I can tell it
> should be possible. $199 is fairly reasonable.

Stripping HDCP for digital recording is in violation of DMCA, is of
questionable legality, and should not be discussed in here.

Aside from that, MythTV has recommended hardware encoders and digital
tuners for the past several years for good reason. Real time encoding
is hard. Capture and proper sync of audio is hard. Hardware encoders
sidestep this issue and do it all for us. Considering this device uses
its own API, and is not automatically supported by including the V4L
API, it is not likely anyone is going to go out of their way to write
support for a framegrabber.


george.galt at gmail

Apr 15, 2010, 10:35 AM

Post #4 of 22 (9280 views)
Permalink
Re: HDMI capture card with linux drivers [In reply to]

> The first thing you would need would be a LOT of storage. I think this device
> creates uncompressed video, difficult to deal with in a Myth type system.
> Compressing it on the fly in software would require a LOT of computing grunt.
>
> _______________________________________________
> mythtv-users mailing list
> mythtv-users [at] mythtv
> http://mythtv.org/cgi-bin/mailman/listinfo/mythtv-users
>

Seems like it may have some form of hardware compression, though it's
not clear. The site says:

On Windows, Blackmagic's full resolution (1920 x 1080) professional
quality compressed HD codec can capture JPEG AVI files in real time
using Premiere Pro. Unlike HDV and DVCPRO HD which uses reduced
resolution 1440 x 1080 video, Blackmagic's Online JPEG maintains the
full resolution 1920 x 1080 resolution of HD video without the huge
file size of uncompressed HD video. Blackmagic's Online JPEG is so
efficient that full motion 1080i HD video can be recorded at only 12
MB per second vs. a massive 119 MB per second for uncompressed HD
video.

Blackmagic's compressed files are so compact, that 1080 HD video can
be captured to a single internal hard disk or easily transported on a
portable Firewire drive! Online JPEG is compatible with Premiere Pro
and After Effects® and can even be used by editors without Blackmagic
capture cards making it one of the most versatile compressed codecs
available.



Words that seem problematic are "Blackmagic's full resolution (1920 x
1080) professional quality compressed HD codec ", which I assume is
proprietary and closed -- though I will note that one of their devices
lists Linux as a compatible OS.

This doesn't mean that there isn't a host of other issues with this
device, but at least it seems like it is doing some form of hardware
compression (though 12MB per second (sic) doesn't seem all that
great).

George
_______________________________________________
mythtv-users mailing list
mythtv-users [at] mythtv
http://mythtv.org/cgi-bin/mailman/listinfo/mythtv-users


raymond at wagnerrp

Apr 15, 2010, 10:39 AM

Post #5 of 22 (9156 views)
Permalink
Re: HDMI capture card with linux drivers [In reply to]

On 4/15/2010 13:35, George Galt wrote:
> On Windows, Blackmagic's full resolution (1920 x 1080) professional
> quality compressed HD codec can capture JPEG AVI files in real time
> using Premiere Pro. Unlike HDV and DVCPRO HD which uses reduced
> resolution 1440 x 1080 video, Blackmagic's Online JPEG maintains the
> full resolution 1920 x 1080 resolution of HD video without the huge
> file size of uncompressed HD video. Blackmagic's Online JPEG is so
> efficient that full motion 1080i HD video can be recorded at only 12
> MB per second vs. a massive 119 MB per second for uncompressed HD
> video.
>

Their software provides realtime compression to mjpeg.
_______________________________________________
mythtv-users mailing list
mythtv-users [at] mythtv
http://mythtv.org/cgi-bin/mailman/listinfo/mythtv-users


beww at beww

Apr 15, 2010, 10:47 AM

Post #6 of 22 (9050 views)
Permalink
Re: HDMI capture card with linux drivers [In reply to]

On Thursday 15 April 2010 11:35:05 am George Galt wrote:
> > The first thing you would need would be a LOT of storage. I think this
> > device creates uncompressed video, difficult to deal with in a Myth type
> > system. Compressing it on the fly in software would require a LOT of
> > computing grunt.
> >
> > _______________________________________________
> > mythtv-users mailing list
> > mythtv-users [at] mythtv
> > http://mythtv.org/cgi-bin/mailman/listinfo/mythtv-users
>
> Seems like it may have some form of hardware compression, though it's
> not clear. The site says:
>
> On Windows, Blackmagic's full resolution (1920 x 1080) professional
> quality compressed HD codec can capture JPEG AVI files in real time
> using Premiere Pro. Unlike HDV and DVCPRO HD which uses reduced
> resolution 1440 x 1080 video, Blackmagic's Online JPEG maintains the
> full resolution 1920 x 1080 resolution of HD video without the huge
> file size of uncompressed HD video. Blackmagic's Online JPEG is so
> efficient that full motion 1080i HD video can be recorded at only 12
> MB per second vs. a massive 119 MB per second for uncompressed HD
> video.
>
> Blackmagic's compressed files are so compact, that 1080 HD video can
> be captured to a single internal hard disk or easily transported on a
> portable Firewire drive! Online JPEG is compatible with Premiere Pro
> and After Effects® and can even be used by editors without Blackmagic
> capture cards making it one of the most versatile compressed codecs
> available.
>
>
>
> Words that seem problematic are "Blackmagic's full resolution (1920 x
> 1080) professional quality compressed HD codec ", which I assume is
> proprietary and closed -- though I will note that one of their devices
> lists Linux as a compatible OS.
>
> This doesn't mean that there isn't a host of other issues with this
> device, but at least it seems like it is doing some form of hardware
> compression (though 12MB per second (sic) doesn't seem all that
> great).

It does seem like they are doing some sort of compression, I guess I missed
that.

Anything that can capture HD from an HDMI port would probably be locked down
pretty tight, as HDCP is the only thing "protecting" HD now.

Of course it might mute some of the cries to close the "analog hole"
(component outputs) if there was a alternative available to the "pirates".

Hypothetically, and theoretically, some of the HDMI "splitter" devices will
output clean video if just one of the ports has HDCP, or so I have heard.



_______________________________________________
mythtv-users mailing list
mythtv-users [at] mythtv
http://mythtv.org/cgi-bin/mailman/listinfo/mythtv-users


ylee at pobox

Apr 15, 2010, 1:44 PM

Post #7 of 22 (9052 views)
Permalink
Re: HDMI capture card with linux drivers [In reply to]

Raymond Wagner <raymond [at] wagnerrp> says:
> Their software provides realtime compression to mjpeg.

. . . which immediately makes the device a nonstarter unless and
until Nvidia sees fit to add MJPEG support to VDPAU. There's a reason
the PVR Companion, whose makers also planned to incorporate MJPEG
encoding into, never made it to the market.

--
Frontend/backend: P4 3.0GHz, 1.5TB software RAID 5 array
Backend: Quad-core Xeon 1.6GHz, 6.6TB sw RAID 6
Video inputs: Four high-definition over FireWire/OTA
Accessories: 47" 1080p LCD, 5.1 digital, and MX-600
_______________________________________________
mythtv-users mailing list
mythtv-users [at] mythtv
http://mythtv.org/cgi-bin/mailman/listinfo/mythtv-users


raymond at wagnerrp

Apr 15, 2010, 5:07 PM

Post #8 of 22 (9022 views)
Permalink
Re: HDMI capture card with linux drivers [In reply to]

On 4/15/2010 16:44, Yeechang Lee wrote:
> Raymond Wagner<raymond [at] wagnerrp> says:
>
>> Their software provides realtime compression to mjpeg.
>>
> . . . which immediately makes the device a nonstarter unless and
> until Nvidia sees fit to add MJPEG support to VDPAU. There's a reason
> the PVR Companion, whose makers also planned to incorporate MJPEG
> encoding into, never made it to the market.
>

Their software... meaning it has nothing to do with the hardware or the
drivers. Besides which, I don't see how VDPAU factors into any of
this. We're talking about difficulty in recording, while VDPAU exists
for playback only.
_______________________________________________
mythtv-users mailing list
mythtv-users [at] mythtv
http://mythtv.org/cgi-bin/mailman/listinfo/mythtv-users


nick.rout at gmail

Apr 15, 2010, 5:29 PM

Post #9 of 22 (8996 views)
Permalink
Re: HDMI capture card with linux drivers [In reply to]

On Fri, Apr 16, 2010 at 12:07 PM, Raymond Wagner <raymond [at] wagnerrp> wrote:
> On 4/15/2010 16:44, Yeechang Lee wrote:
>>
>> Raymond Wagner<raymond [at] wagnerrp>  says:
>>
>>>
>>> Their software provides realtime compression to mjpeg.
>>>
>>
>>  . . . which immediately makes the device a nonstarter unless and
>> until Nvidia sees fit to add MJPEG support to VDPAU. There's a reason
>> the PVR Companion, whose makers also planned to incorporate MJPEG
>> encoding into, never made it to the market.
>>
>
> Their software... meaning it has nothing to do with the hardware or the
> drivers.  Besides which, I don't see how VDPAU factors into any of this.
>  We're talking about difficulty in recording, while VDPAU exists for
> playback only.

And I think Yeechang meant that even if you can usefully record this
device's HD MJPEG stream, unless you have some hardware assistance
from the likes of vdpau, it's going to be a difficult task to get it
onto your screen.
_______________________________________________
mythtv-users mailing list
mythtv-users [at] mythtv
http://mythtv.org/cgi-bin/mailman/listinfo/mythtv-users


kevin at familyross

Apr 15, 2010, 5:49 PM

Post #10 of 22 (8986 views)
Permalink
Re: HDMI capture card with linux drivers [In reply to]

Nick Rout wrote:
> On Fri, Apr 16, 2010 at 12:07 PM, Raymond Wagner <raymond [at] wagnerrp>
> wrote:
> > On 4/15/2010 16:44, Yeechang Lee wrote:
> >>
> >> Raymond Wagner<raymond [at] wagnerrp>  says:
> >>
> >>>
> >>> Their software provides realtime compression to mjpeg.
> >>>
> >>
> >>  . . . which immediately makes the device a nonstarter unless and
> >> until Nvidia sees fit to add MJPEG support to VDPAU. There's a
> reason
> >> the PVR Companion, whose makers also planned to incorporate MJPEG
> >> encoding into, never made it to the market.
> >>
> >
> > Their software... meaning it has nothing to do with the hardware or
> the
> > drivers.  Besides which, I don't see how VDPAU factors into any of
> this.
> >  We're talking about difficulty in recording, while VDPAU exists for
> > playback only.
>
> And I think Yeechang meant that even if you can usefully record this
> device's HD MJPEG stream, unless you have some hardware assistance
> from the likes of vdpau, it's going to be a difficult task to get it
> onto your screen.

Actually if it's the software doing the MJPEG compression, that implies that
the output from the device is uncompressed video. That would mean the only
problem you would have is finding enough hard drive space to put it, and
drives fast enough to keep up with real-time writing and reading
simultaneously. The CPU wouldn't be the bottleneck, nor would the PCIe bus
or the video card.

_______________________________________________
mythtv-users mailing list
mythtv-users [at] mythtv
http://mythtv.org/cgi-bin/mailman/listinfo/mythtv-users


nick.rout at gmail

Apr 15, 2010, 5:51 PM

Post #11 of 22 (8940 views)
Permalink
Re: HDMI capture card with linux drivers [In reply to]

On Fri, Apr 16, 2010 at 12:49 PM, Kevin Ross <kevin [at] familyross> wrote:
> Nick Rout wrote:
>> On Fri, Apr 16, 2010 at 12:07 PM, Raymond Wagner <raymond [at] wagnerrp>
>> wrote:
>> > On 4/15/2010 16:44, Yeechang Lee wrote:
>> >>
>> >> Raymond Wagner<raymond [at] wagnerrp>  says:
>> >>
>> >>>
>> >>> Their software provides realtime compression to mjpeg.
>> >>>
>> >>
>> >>  . . . which immediately makes the device a nonstarter unless and
>> >> until Nvidia sees fit to add MJPEG support to VDPAU. There's a
>> reason
>> >> the PVR Companion, whose makers also planned to incorporate MJPEG
>> >> encoding into, never made it to the market.
>> >>
>> >
>> > Their software... meaning it has nothing to do with the hardware or
>> the
>> > drivers.  Besides which, I don't see how VDPAU factors into any of
>> this.
>> >  We're talking about difficulty in recording, while VDPAU exists for
>> > playback only.
>>
>> And I think Yeechang meant that even if you can usefully record this
>> device's HD MJPEG stream, unless you have some hardware assistance
>> from the likes of vdpau, it's going to be a difficult task to get it
>> onto your screen.
>
> Actually if it's the software doing the MJPEG compression, that implies that
> the output from the device is uncompressed video.  That would mean the only
> problem you would have is finding enough hard drive space to put it, and
> drives fast enough to keep up with real-time writing and reading
> simultaneously.  The CPU wouldn't be the bottleneck, nor would the PCIe bus
> or the video card.

Or find a hardware h264 encoder?

Are there any for linux?

>
> _______________________________________________
> mythtv-users mailing list
> mythtv-users [at] mythtv
> http://mythtv.org/cgi-bin/mailman/listinfo/mythtv-users
>
_______________________________________________
mythtv-users mailing list
mythtv-users [at] mythtv
http://mythtv.org/cgi-bin/mailman/listinfo/mythtv-users


raymond at wagnerrp

Apr 15, 2010, 6:46 PM

Post #12 of 22 (8994 views)
Permalink
Re: HDMI capture card with linux drivers [In reply to]

On 4/15/2010 20:49, Kevin Ross wrote:
> Actually if it's the software doing the MJPEG compression, that implies that
> the output from the device is uncompressed video. That would mean the only
> problem you would have is finding enough hard drive space to put it, and
> drives fast enough to keep up with real-time writing and reading
> simultaneously. The CPU wouldn't be the bottleneck, nor would the PCIe bus
> or the video card.
>

You're talking about 100-180MB/s depending on resolution and framerate.
You do NOT want to store this uncompressed to disk.
_______________________________________________
mythtv-users mailing list
mythtv-users [at] mythtv
http://mythtv.org/cgi-bin/mailman/listinfo/mythtv-users


ylee at pobox

Apr 15, 2010, 8:47 PM

Post #13 of 22 (9000 views)
Permalink
Re: HDMI capture card with linux drivers [In reply to]

Raymond Wagner <raymond [at] wagnerrp> says:
> Besides which, I don't see how VDPAU factors into any of this.
> We're talking about difficulty in recording, while VDPAU exists for
> playback only.

On the contrary. What's the point of recording something you can't
play back?

In retrospect today's HD-PVR would have been more or less pointless to
own before sometime in 2007 or 2008, because no existing PC would've
been fast enough to play its high-definition h.264 encodings.[!] Sure,
it could've been used to encode HD into SD video, but Hauppauge and
other vendors already sold a wide range of SD encoders that could do
that.[*] Even in mid-2008, Robert McNamara, John Poet, and other
HD-PVR early adopters reported that, at maximum quality, its output
sometimes stumped even the fastest Core 2 Duo boxes. VDPAU, and its
full support for h.264 hardware-acelerated decoding and rendering,
could not have come along any sooner than it did.

[*] That's my understanding, at least; the HD-PVR is the first
Hauppauge or v4l-using device I've ever used.

[!] To the extent that people on mythtv-users thought in detail about
what a true "HD capture card for MythTV" would look like, we imagined
it would be a) something that produced MPEG-2 output or b) some sort
of Linux-compatible CableCARD adapter.

--
Frontend/backend: P4 3.0GHz, 1.5TB software RAID 5 array
Backend: Quad-core Xeon 1.6GHz, 6.6TB sw RAID 6
Video inputs: Four high-definition over FireWire/OTA
Accessories: 47" 1080p LCD, 5.1 digital, and MX-600
_______________________________________________
mythtv-users mailing list
mythtv-users [at] mythtv
http://mythtv.org/cgi-bin/mailman/listinfo/mythtv-users


ylee at pobox

Apr 15, 2010, 9:07 PM

Post #14 of 22 (8895 views)
Permalink
Re: HDMI capture card with linux drivers [In reply to]

Raymond Wagner <raymond [at] wagnerrp> says:
> Their software... meaning it has nothing to do with the hardware or
> the drivers.

That's can't be right; my understanding is that it's impossible for a
general-purpose consumer-priced computer today to real-time encode HD
video into high-quality h.264. (Otherwise someone by now would've
written such an encoder and turn any simple hardware framegrabber into
a HD-PVR equivalent.) Or am I mistaken?

Even if I am mistaken and such a thing is practical, I certainly
prefer the HD-PVR approach for its convenience, flexibility, and
simplicity. While going the all-software route is sometimes
desirable,[*] VDPAU and HD-PVR have shown that inexpensive custom
silicon can sometimes do things that general-purpose hardware just
can't replicate.

[*] Such as Linux software RAID versus fakeRAID cards. Even Areca,
3Ware, and other good-quality true-RAID cards share fakeRAID's
disadvantage in terms of vendor/model lock-in potential, and they
haven't offered better performance than mdadm RAID on a non-ancient
server in a long time.

--
Frontend/backend: P4 3.0GHz, 1.5TB software RAID 5 array
Backend: Quad-core Xeon 1.6GHz, 6.6TB sw RAID 6
Video inputs: Four high-definition over FireWire/OTA
Accessories: 47" 1080p LCD, 5.1 digital, and MX-600
_______________________________________________
mythtv-users mailing list
mythtv-users [at] mythtv
http://mythtv.org/cgi-bin/mailman/listinfo/mythtv-users


raymond at wagnerrp

Apr 15, 2010, 10:07 PM

Post #15 of 22 (8878 views)
Permalink
Re: HDMI capture card with linux drivers [In reply to]

On 4/16/2010 00:07, Yeechang Lee wrote:
> Raymond Wagner<raymond [at] wagnerrp> says:
>
>> Their software... meaning it has nothing to do with the hardware or
>> the drivers.
>>
> That's can't be right; my understanding is that it's impossible for a
> general-purpose consumer-priced computer today to real-time encode HD
> video into high-quality h.264. (Otherwise someone by now would've
> written such an encoder and turn any simple hardware framegrabber into
> a HD-PVR equivalent.) Or am I mistaken?
>

I'm saying it is their software that captures to MJPEG, not the
hardware, not the linux drivers. If MythTV were to support this device,
it would use its own encoding mechanism, be that RTJPEG, MPEG4, H264, or
whatever. VDPAU support would not factor into the equation, since the
fact that the Windows software uses MJPEG has no bearing what-so-ever on
what MythTV would do.

Furthermore, compression is almost always asymmetric, with compression
taking far longer than decompression. Any machine capable of capturing
and compressing such video would easily be able to decompress it later.
Hardware acceleration would not be necessary.
_______________________________________________
mythtv-users mailing list
mythtv-users [at] mythtv
http://mythtv.org/cgi-bin/mailman/listinfo/mythtv-users


Douglas_Peale at comcast

Apr 15, 2010, 10:24 PM

Post #16 of 22 (8876 views)
Permalink
Re: HDMI capture card with linux drivers [In reply to]

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

Raymond Wagner wrote:
> On 4/16/2010 00:07, Yeechang Lee wrote:
>> Raymond Wagner<raymond [at] wagnerrp> says:
>>
>>> Their software... meaning it has nothing to do with the hardware or
>>> the drivers.
>>>
>> That's can't be right; my understanding is that it's impossible for a
>> general-purpose consumer-priced computer today to real-time encode HD
>> video into high-quality h.264. (Otherwise someone by now would've
>> written such an encoder and turn any simple hardware framegrabber into
>> a HD-PVR equivalent.) Or am I mistaken?
>>
>
> I'm saying it is their software that captures to MJPEG, not the
> hardware, not the linux drivers. If MythTV were to support this device,
> it would use its own encoding mechanism, be that RTJPEG, MPEG4, H264, or
> whatever. VDPAU support would not factor into the equation, since the
> fact that the Windows software uses MJPEG has no bearing what-so-ever on
> what MythTV would do.
>
> Furthermore, compression is almost always asymmetric, with compression
> taking far longer than decompression. Any machine capable of capturing
> and compressing such video would easily be able to decompress it later.
> Hardware acceleration would not be necessary.
> _______________________________________________
> mythtv-users mailing list
> mythtv-users [at] mythtv
> http://mythtv.org/cgi-bin/mailman/listinfo/mythtv-users
>
Lets do a bit of math here.
1920 pixels * 1080 pixels * 3 bytes * 30 frames/second = 186,624,000
bytes/second.
There are very few hard drives that can be written that fast.
Your computer could do nothing else but write the disk, so there is no
possibility of encoding while recording.
So you want to record a 2 hour movie, that is 186,624,000 * 60 * 60 * 2
= 1,343,692,800,000 bytes.
So it would require most of one of the largest hard drives available
today just to store the unencrypted file.

This is not really practical.
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.4.9 (GNU/Linux)
Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org

iEYEARECAAYFAkvH9IkACgkQe5tReOauESoS+gCfYqdshYC3NCer72oYBhrujPPb
KZ8AnRYanfWI9nrkUWjpIyh7qX+owTCG
=x7tq
-----END PGP SIGNATURE-----
_______________________________________________
mythtv-users mailing list
mythtv-users [at] mythtv
http://mythtv.org/cgi-bin/mailman/listinfo/mythtv-users


raymond at wagnerrp

Apr 15, 2010, 10:28 PM

Post #17 of 22 (8849 views)
Permalink
Re: HDMI capture card with linux drivers [In reply to]

On 4/16/2010 01:24, Douglas Peale wrote:
> Your computer could do nothing else but write the disk, so there is no
> possibility of encoding while recording.
>

Why not? Obviously the BlackMagic Windows software already performs
this impossible task of encoding to MJPEG on the fly.
_______________________________________________
mythtv-users mailing list
mythtv-users [at] mythtv
http://mythtv.org/cgi-bin/mailman/listinfo/mythtv-users


Douglas_Peale at comcast

Apr 15, 2010, 11:15 PM

Post #18 of 22 (8863 views)
Permalink
Re: HDMI capture card with linux drivers [In reply to]

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

Raymond Wagner wrote:
> On 4/16/2010 01:24, Douglas Peale wrote:
>> Your computer could do nothing else but write the disk, so there is no
>> possibility of encoding while recording.
>>
>
> Why not? Obviously the BlackMagic Windows software already performs
> this impossible task of encoding to MJPEG on the fly.
> _______________________________________________
> mythtv-users mailing list
> mythtv-users [at] mythtv
> http://mythtv.org/cgi-bin/mailman/listinfo/mythtv-users
>

Unless they are using a raid system, they are not writing the
uncompressed file directly to disk.

See current performance figures for 2 TB hard drives:
http://www.storagereview.com/western_digital_caviar_black_review_2tb

So, they must be doing real time compression.

Are you sure they are doing this in software? I'm not aware of any
software that can handle HD compression in real time on a PC. Unless of
course you don't care about the quality.

Non real time compression is doomed because it must buffer to disk since
there is no way you are going to get 1.3 TB of ram in a system. And in
order to use a disk buffer, you must simultaneously write the
uncompressed data to disk (already an impossibility with current
drives), read that uncompressed data, compress it, and write it back out
to the drive.

I missed the beginning of this discussion. I understand you want to
record HDMI signals. I'm assuming you want to do this because that is
what you get out of your cable box. You do realize that this data is
encrypted don't you? How do you plan on decrypting it? The only time it
might not be encrypted would be if it was broadcast in clear QAM in the
first place. In that case you would be much better off just saving the
already compressed data before it gets uncompressed and sent over the
HDMI cable.
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.4.9 (GNU/Linux)
Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org

iEYEARECAAYFAkvIAJQACgkQe5tReOauESrjngCcCCq1JeIBMlmfM7Q/vCr/VzhN
VHIAn1dbJeQCH6VcATSFHAJv8bD3E+5Y
=JTlO
-----END PGP SIGNATURE-----
_______________________________________________
mythtv-users mailing list
mythtv-users [at] mythtv
http://mythtv.org/cgi-bin/mailman/listinfo/mythtv-users


Douglas_Peale at comcast

Apr 15, 2010, 11:58 PM

Post #19 of 22 (8869 views)
Permalink
Re: HDMI capture card with linux drivers [In reply to]

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

Douglas Peale wrote:
> Raymond Wagner wrote:
> I missed the beginning of this discussion. I understand you want to
> record HDMI signals. I'm assuming you want to do this because that is
> what you get out of your cable box. You do realize that this data is
> encrypted don't you? How do you plan on decrypting it? The only time it
> might not be encrypted would be if it was broadcast in clear QAM in the
> first place. In that case you would be much better off just saving the
> already compressed data before it gets uncompressed and sent over the
> HDMI cable.

Never mind, I found the history of this thread.

It turns out that the HDMI is doing some compression on the data, they
are using YUV 4:2:2 which means they are throwing away half of the color
information.

So the calculation is more like (1920 * 1080) pixels * 10 bits/sample *
2 samples/pixel * 30 frames/sec * 1/8 bytes/bit =155,520,000 bytes/second.
Still to much for a single drive. They do recommend an array though.

This card is fine for video editing, but useless for a PVR. This device
does not decrypt HDMI signals, cable boxes will be downresing their
component outputs, and anything that is not encrypted or downres, can be
captured with a clear QAM tuner.
_______________________________________________
mythtv-users mailing list
mythtv-users [at] mythtv
http://mythtv.org/cgi-bin/mailman/listinfo/mythtv-users

-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.4.9 (GNU/Linux)
Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org

iEYEARECAAYFAkvICqoACgkQe5tReOauESoDPACfW53cQm4uP7Uk6C2bs4Ks9xZf
+LMAniPu4KAvbUwROhdCcJ27HISFmWds
=f9q4
-----END PGP SIGNATURE-----
_______________________________________________
mythtv-users mailing list
mythtv-users [at] mythtv
http://mythtv.org/cgi-bin/mailman/listinfo/mythtv-users


raymond at wagnerrp

Apr 16, 2010, 1:03 AM

Post #20 of 22 (8842 views)
Permalink
Re: HDMI capture card with linux drivers [In reply to]

On 4/16/2010 02:15, Douglas Peale wrote:
> -----BEGIN PGP SIGNED MESSAGE-----
> Hash: SHA1
>
> Raymond Wagner wrote:
>
>> On 4/16/2010 01:24, Douglas Peale wrote:
>>
>>> Your computer could do nothing else but write the disk, so there is no
>>> possibility of encoding while recording.
>>>
>>>
>> Why not? Obviously the BlackMagic Windows software already performs
>> this impossible task of encoding to MJPEG on the fly.
>> _______________________________________________
>> mythtv-users mailing list
>> mythtv-users [at] mythtv
>> http://mythtv.org/cgi-bin/mailman/listinfo/mythtv-users
>>
>>
> Unless they are using a raid system, they are not writing the
> uncompressed file directly to disk.
>

Correct, their software compressed to MJPEG for storage in real time.
Your original claim was that the CPU would be so busy trying to write to
the disk, that it would not have the power to compress the feed to
something smaller. That is false.

> Are you sure they are doing this in software? I'm not aware of any
> software that can handle HD compression in real time on a PC. Unless of
> course you don't care about the quality.
>

'HD compression' is an absolutely meaningless term if you don't specify
the codec in use. Huffyuv is extremely fast, such that the author's
400MHz Celeron was able to compress DVD video (480p30) in real time.
Any Core2 or Athlon64 should be able to handle 1080i60 in real time.
MJPEG is almost as fast, if a bit lossy and so less suited for video
editing.
_______________________________________________
mythtv-users mailing list
mythtv-users [at] mythtv
http://mythtv.org/cgi-bin/mailman/listinfo/mythtv-users


mythtv-list at dinkum

Apr 16, 2010, 1:56 AM

Post #21 of 22 (8923 views)
Permalink
Re: HDMI capture card with linux drivers [In reply to]

On 16 Apr 2010, at 09:03, Raymond Wagner wrote:

> On 4/16/2010 02:15, Douglas Peale wrote:
>> -----BEGIN PGP SIGNED MESSAGE-----
>> Hash: SHA1
>>
>> Raymond Wagner wrote:
>>
>>> On 4/16/2010 01:24, Douglas Peale wrote:
>>>
>>>> Your computer could do nothing else but write the disk, so there is no
>>>> possibility of encoding while recording.
>>>>
>>>>
>>> Why not? Obviously the BlackMagic Windows software already performs
>>> this impossible task of encoding to MJPEG on the fly.
>>> _______________________________________________
>>> mythtv-users mailing list
>>> mythtv-users [at] mythtv
>>> http://mythtv.org/cgi-bin/mailman/listinfo/mythtv-users
>>>
>>>
>> Unless they are using a raid system, they are not writing the
>> uncompressed file directly to disk.
>>
>
> Correct, their software compressed to MJPEG for storage in real time. Your original claim was that the CPU would be so busy trying to write to the disk, that it would not have the power to compress the feed to something smaller. That is false.

I've used several of Blackmagic's HDSDI cards, this one is much the same but with HDMI instead of HDSDI input, the software happily compresses to a choice of formats from uncompressed through to h264, there are a couple of blackmagic codecs supplied that match up to the capture formats the card can handle (4:4:4, 4:2:2, 4:2:0, 8bit, 10bit etc.), they appear to be some sort of lossless compression, I'm not certain but I've always thought these used hardware compression on the cards. There's no mpeg2 or h264 hardware but these are broadcast TV cards and no-one would use those codecs for broadcast capture.

And yes you usually need a raid array to capture this card's output, three striped middle of the road 7200rpm disks will cover pretty much everything, I have two Samsung 501LJ's in this machine and they manage ok for 1080i25 at 8 bit 4:2:2 can't do 4:4:4 or 10 bit.

The Linux drivers are news to me but these guys are the most innovative and helpful broadcast capture hardware people I've ever worked with, their hardware is not always top notch but they have added features to drivers for me a couple of times quickly and with no fuss. They were the first to have a capture card that worked with Windows & Mac, everyone else made you buy two cards, with the number of dual boot Mac Pro's around in TV production houses they are really useful. If they have added Linux support across their range that's great, that gives me some ideas...

Andre
>
>> Are you sure they are doing this in software? I'm not aware of any
>> software that can handle HD compression in real time on a PC. Unless of
>> course you don't care about the quality.
>>
>
> 'HD compression' is an absolutely meaningless term if you don't specify the codec in use. Huffyuv is extremely fast, such that the author's 400MHz Celeron was able to compress DVD video (480p30) in real time. Any Core2 or Athlon64 should be able to handle 1080i60 in real time. MJPEG is almost as fast, if a bit lossy and so less suited for video editing.

Actually various MJPEG flavours used to be used a lot in editing, at very high bit rates, 50Mb/s for SD for example, because each frame is compressed separately simple cuts give no quality loss and for any other process only frames affected need to be de-compressed and re-compressed. These days there are a lot of choice of codecs that compress and de-compress extremely quickly, are low loss for editing or transport across studios, many are based on H264 but bear almost no resemblance to final broadcast H264 that comes OTA or OTW. For example Quicktime Prores is a form of H264 at 140Mb/s or 220M/s for HD, this is commonly used in HDTV editing, this can be produced from one these cards in the background on a Mac Pro while editing is going on.

Bottom line is, this card is not aimed at domestic systems.

Andre
_______________________________________________
mythtv-users mailing list
mythtv-users [at] mythtv
http://mythtv.org/cgi-bin/mailman/listinfo/mythtv-users


mikep at randomtraveller

Apr 16, 2010, 4:35 AM

Post #22 of 22 (8854 views)
Permalink
Re: HDMI capture card with linux drivers [In reply to]

Douglas Peale wrote:
>
> Lets do a bit of math here.
> 1920 pixels * 1080 pixels * 3 bytes * 30 frames/second = 186,624,000
> bytes/second.
> There are very few hard drives that can be written that fast.
> Your computer could do nothing else but write the disk, so there is no
> possibility of encoding while recording.
> So you want to record a 2 hour movie, that is 186,624,000 * 60 * 60 * 2
> = 1,343,692,800,000 bytes.
> So it would require most of one of the largest hard drives available
> today just to store the unencrypted file.
>
It's not impossible. In 1997 I worked, briefly, on software for a professional
video recorder/editor (which ran under a customised version of Windows NT4.0!)
which offered recording rates up to 9 Gb/minute: how they did this with the
hardware available at the time I have no idea, but I saw it working, so is
obviously possible[1].

However, using a hardware encoder means that you write a much smaller stream to
disk, which is obviously more sensible. You just have to pick your hardware and
a suitable codec :)

[1] As I recall, it buffered to disk at one end while the other end frantically
wrote it out to broadcast-quality betamax tapes. Go figure.

--

Mike Perkins

_______________________________________________
mythtv-users mailing list
mythtv-users [at] mythtv
http://mythtv.org/cgi-bin/mailman/listinfo/mythtv-users

MythTV users RSS feed   Index | Next | Previous | View Threaded
 
 


Interested in having your list archived? Contact Gossamer Threads
 
  Web Applications & Managed Hosting Powered by Gossamer Threads Inc.