mpeg2 50mbps capture questions

[the1selecta]

Hi,

We have been given various different vhs, betamax, hi8 etc to capture. We have been advised to capture at 50mbps as mpeg2 compression in realtime. Could anyone recommend the most efficient setup for doing this (any particularly good vhs players, ways to play betamax, mpeg capture cards etc)? The PC wil l be 320gb ATA-100 HDD, 4Gb Ram, latest 3ghz Pentium. Idealy we want to capture at the same length or quicker than the analogue footage (so 1hr of footage takes 1 hr to capture or less)

I understand that to roughly work out the size of the file is:

50 mbps / 8 = 6.25 Mbps x 3600secs (1hr) = 22.5Gb per hour of footage

Thanks,

Steve

[edDV]

This is a non-trivial project and a 3GHz Pentium is a fairly weak platform. Encoding will have to be done in hardware.

Do you have a budget to do this right? Do you have players that are fully serviced? Quality capture will require a TBC or Frame Sync.

For 50 Mb/s MPeg2, are they looking for 4:2:2 or 4:2:0 (YV12)?

[olyteddy]

Idealy we want to capture at the same length or quicker than the analogue footage (so 1hr of footage takes 1 hr to capture or less)

That's not gonna happen either. You'll have to add in the time to rewind and change tapes. And no tape format will play any faster than real time.

[the1selecta]

Intel Core i3 Processor 540 (3.06GHz, 4MB)
4096MB 1333 MHz Dual Channel DDR3 SDRAM [4x1024]
1TB Serial ATA (7200RPM) Hard Drive

Yes, there is a budget to do this, it is moderate

We realise we have to rewind and change tapes - currently putting in unit costs for the capture itself

They looking for 4:2:2

Would realtime capturing for these formats be realistic?

[aedipuss]

sounds like they want a pro using broadcast quality equipment like the sony XDCAM HD422 Deck to capture with. that's about the only way you are going to get mpeg-2 4:2:2 at 50mbps.

[edDV]

50 Mb/s is overkill for SD MPeg2 but it can be done. For comparison 50 Mb/s is the top Blu-Ray rate.

Normal practice would be to use a quality TBC/Frame Sync and capture uncompressed 4:2:2, then software encode on a second pass. Real time hardware encoders that encode at 50 Mb/s 4:2:2 are going to be difficult to find. Real time software encoding is possible with Mainconcept's Reference encoder.
http://www.mainconcept.com/products/apps-plug-ins/transcoding/reference.html

Sony's IMX format (now called XDCAM IMX, aka SMPTE D-10 format) is SD 4:2:2 MPeg2, I frame only and 50 Mb/s is the top rate. The Mainconcept Reference encoder will real time capture to IMX. Check with Mainconcept to see if an i3 has enough grunt. They could also recommend a capture card.

[aedipuss]

sorry i should have been more specific. the sony PDW-1500 is the deck i was referring to.

[edDV]

Yes we are talking pro formats and budgets here. I hope the1selecta didn't low bid this project.

But the Mainconcept Ref MPeg codec is much cheaper vs. IMX hardware. This assumes well tuned playback decks and a good hardware TBC.

[the1selecta]

Hi, thanks for all the advice. The Mainconcept Ref MPEG codec sounds like a good option, but ideally we want to capture directly as MPEG 2 50mb/sec.

We have been recommended the Matrox RT X2 that captures to MPEG 2 50mb/sec but is I-Frame only and the format is in an avi wrapper - ideally we need one that is MPEG 2 for broadcast archiving. Any recommendations, bar spending £10,000 on a Sony?

[jagabo]

This is a non-trivial project and a 3GHz Pentium is a fairly weak platform. Encoding will have to be done in hardware.

At 50 Mb/s he's likely to be doing all I frame caps. A 3 GHz P4 will probably work for that.

Nevermind, I see he will be using a Matrox RT X2. Guess he'll have to check their requirements.

[the1selecta]

jagabo, I didn't state we are using it - it was a recommendation. We are looking at various solutions. Their requirements are 50 mb/sec MPEG 2 for archival purposes of low quality vhs/betamax footage. They have not specified I-frame or Long GOP. We will of course check with them - trying to gather as much info as poss on it.

[jagabo]

At 50 MB/s you might as well use all I frame. That's nearly twice the bitrate of DV which is all I frame.

[edDV]

Hi, thanks for all the advice. The Mainconcept Ref MPEG codec sounds like a good option, but ideally we want to capture directly as MPEG 2 50mb/sec.

We have been recommended the Matrox RT X2 that captures to MPEG 2 50mb/sec but is I-Frame only and the format is in an avi wrapper - ideally we need one that is MPEG 2 for broadcast archiving. Any recommendations, bar spending £10,000 on a Sony?

You can rent the Sony in prime markets. I'd probably have to drive into San Francisco.

The Mainconcept Ref will software capture encode. Just not sure of CPU requirement. The higher the bit rate, the lower the CPU load.

Can't offer any input on the Matrox.

[vhelp]

The matrix mpeg-2 codec is an avi container, i-frame, 4:2:2. And i'm currently using it at 20 kbits/s, in my directv captures..so far so good. Much smaller filesize then dv and bitrate, plus, you get 422 instead of 420, can't complain.

You might be able to get software (realtime) encode as already suggested above w/ mainconcepts, but I think there is a limit on the bitrate if you are going by standards via profile/levels.

using TMPGenc as a guide for these profiles.

MP@ML (or, main@main) 15 kbits/s=116mb, 4:2:0
MP@HL (or, main@high) 50 kbits/s=380mb, up to 80 kbit/s=607mb, 4:2:0
high profile and high-1440 level, you can go 15 kbits/s, 4:2:0 and 4:2:2 no problem

I tested a minute encode from my matrox codec (above), and it was realtime +/- 8 secs, I have a slow computer. In TMPGenc, for realtime performance, set the Motion Search Procession to motion estimation (fast) and at 50 kbit/s it might give you near lossless if the source has no post compression/pixelation artifacts already. That's the setup i've used, though not the 50 kbits/s bitrate.

-vhelp 5431