Video on PPC Macs

[tachyon]

Hi 68kmla folks,

I tried asking this on the macgurus forums a while ago, but never got a great response.

How come my 5500/225 with 128MB RAM can record smoother video than a 7600/200 with 384MB RAM?

Is it the faster IDE hard drive in the 5500?

I tried recording directly to RAM, but I got unusably out of synch audio on the 7600.

I would have thought the 604 processor would make it sweet.

Will adding a SCSI-2 drive help with the frame rate?

 

[tomlee59]

I've never done an apples-to-apples test of those two particular models, but here are some general factors that could make a difference:

1) Details of the video subsystems and CPU type and speed. The 604 is not a huge leap beyond the 603ev, as it turns out.

2) As you mentioned, the speed of the hard drives can make a difference. More important, capture to a defragged partition (preferably freshly wiped), or you can have spectacularly lousy results.

3) The OS: 8.6 is generally better than 8.1 for vidcap, for example.

4) Turn off networking and disable all other apps/processes that may compete with capture. Don't even move the mouse during capture.

5) Turn off VM. Failure to do so is a common source of bad sync.

6) Other oddball tidbits: With some model/OS combinations, you even have to move the capture window to a particular corner of the screen (e.g., lower right) to improve capture performance.

 

[alk]

Do you have L2 cache in either machine?

Peace,

Drew

 

[tachyon]

thanks folks.

The 7600 has at least 256MB L2 Cache. The 5500 is... stock, so whatever was standard (I can't remember)

Next question; what codec do you use? The list is so long. Motion-JPEG seems to give good results.

I don't care about file size, I can move the movies to a faster Mac and compress the video later... I just want it to capture as best as it can. Anyone else around that used to use Adobe Premiere or Avid Videoshop?

 

[bluekatt]

er i think you mean 256k l2 cache if it has 256 mb ram chach it can out perform a G4

 

[tomlee59]

Yes, if you truly have no HD space constraints, compress as little as possible (the more time the mac has to spend compressing, the less power it has left over to do actual capture).

MJPEG is a good, simple format. Depending on settings, be prepared for 50-100MB (yes, megabytes) per minute.

 

[JWG Design]

I have had good results capturing 320x240 videos using the Component Video codec. It digitizes in 16-bit YUV format. I don't think there is any compression being applied, so the speed of your processor has very little to do with performance. IIRC, I was capturing ~30fps on a Quadra 840av when I had a fast hard drive installed (Quantum Viking II).

The MJPEG and JPEG codecs use compression, which adds CPU overhead. Those are best suited to capture cards that have on-board hardware codecs (ie. VideoVision Studio).

If you want to keep interlacing intact, try increasing the height to 480 (576 for PAL). The proportions will be off, but you can stretch it back out to full screen during playback to fix that.

 

[Maccess]

IIRC there is an extension you'll have to find that fixes that issue of Sound being out of Sync with Video on non-Performa Power Macs. There's also another extension that you need if you're using a PCI IDE card.

Try searching for "AV PCI Mac Sync Extension"

 

[Temetka]

What would it take to capture 800x600 @30fps?

Think my 500MHz G3 8500 could do it?

It's got 576MB of RAM and a PCI Radeon.

'Twould be cool.

 

[JWG Design]

The accepted desktop video resolutions have been NTSC at 640x480 or PAL at 768x576. Other resolutions simply divided one (or both) of the dimensions in half to reduce data size.

Television standards do not have a resolution of 800x600. Your computer would have to create extra pixels. The results would be bad - slow frame rate and jagged image.

If you had a HDV camera and a FireWire card in your Powermac, then you shouldn't have any trouble transferring 720p or 1080i High-Def video into your Mac. Editing it would be a different story. Apple recommends a 1GHz G4 for HDV editing in iMovie HD.

 

[tomlee59]

What JWG Design said.

You may wish to add a gigundus FW drive -- DV captures will chew up disk space at the rate of a couple hundred megabytes (yes, megabytes) per minute.

Editing will indeed be painfully slow on that machine, as will transcoding the result into any other (delivery) format, so unless you have the patience of a saint, you will quickly grow impatient with the G3's limitations as a video editing machine. That said, I've used my G3 for creating VCDs from live sources from time to time. It's ok for short clips; feature-length films is a whole 'nother thing...

 

[JWG Design]

I don't have any experience with HDV, but I think it uses the same 25Mbps data rate as regular DV. The trouble with HDV is that it uses heavier MPEG compression instead of the simpler compression used in DV.

I have had success capturing and editing DV with iMovie 1 (2?) on a Powermac 8500/120. I will say that my Pismo and Sawtooth are much better at editing DV.

I think the extension referenced earlier might be called the PCI Timing Extension.

 

[tachyon]

If you search on "Everyone's Favorite Search Engine" for "AV PCI Mac Sync Extension" then this thread is the only search result.

If you search for "PCI Timing Extension" there is a reference on

http://www.zone6400.com/L2G3_spec_comparison.html