Getting Started, Documentation, Tips & Tricks

in a perfect world, what I'd like is to capture full res NTSC from my 250MHz R12K O2 in rice, or huffyuv, or one of the other favored lossless video compression formats. what I'm trying to do with the constraints I'm working with, is record in either MV using RLE24, or quicktime animation with full resolution NTSC. what I can't even is just plain record full resolution NTSC with no compression at all.

It looks like the comp option for dmrecord is there because they planned to add that feature later, but where it is now, it only accepts jpeg. so I look at avcapture. when I try anything with avcapture I get packing error, and when I specify -d 3 for vid device 3 (s-video) that fails before the packing has time to fail. I'd love to run avcapture -B which is a disk benchmark because whenever I run diskperf -W I get like 2MB on a 36GB 10K drive.

media recorder's nice, but I can't even get it to capture uncompressed without it dropping so many frames that the result video is choppy as heck.

I'd really like to do this without resorting to mjpeg, but can someone remind me what the max bitrate is for ICE compression?

does anyone have any advice on uncompressed vid cap on an O2?

TeeTylerToe wrote: in a perfect world, what I'd like is to capture full res NTSC from my 250MHz R12K O2 in rice, or huffyuv, or one of the other favored lossless video compression formats. what I'm trying to do with the constraints I'm working with, is record in either MV using RLE24, or quicktime animation with full resolution NTSC. what I can't even is just plain record full resolution NTSC with no compression at all.

It looks like the comp option for dmrecord is there because they planned to add that feature later, but where it is now, it only accepts jpeg. so I look at avcapture. when I try anything with avcapture I get packing error, and when I specify -d 3 for vid device 3 (s-video) that fails before the packing has time to fail. I'd love to run avcapture -B which is a disk benchmark because whenever I run diskperf -W I get like 2MB on a 36GB 10K drive.

media recorder's nice, but I can't even get it to capture uncompressed without it dropping so many frames that the result video is choppy as heck.

I'd really like to do this without resorting to mjpeg, but can someone remind me what the max bitrate is for ICE compression?

does anyone have any advice on uncompressed vid cap on an O2?

You must use the "two fields" option, otherwise you will probably get dropped frames and an error during conversion. And I think Ian Mapleson recommends 3Mb constant bit rate, but you must set that option last before starting the record, due to a bug in mediarecorder. And from experience, there are some sources like VHS that the O2 just doesnt like - I have VHS videos I tried to record where the O2 always drops a frame in exactly the same places no matter how many times I try - probably due to a glitch in the original recording.

this isn't a dropped frame here or there, this one step away from a slideshow.

I'm thinking about doing a dd benchmark piped into time to check bandwidth, lemme start up the O2 and see what error I was getting from avcapture.

"cannot set path packing: VL: bad value passed as parameter"

ok, after further investigation, the O2 works pretty fantastically at capturing uncompressed video. it's more then happy to capture full resolution NTSC to your heart's content.

not only that, it'll encode that captured uncompressed video to mjpeg at just about realtime.

what it absolutely refused unconditionally to do, is play back any kind of uncompressed full frame video at any framerate above 5fps... I should probably try mplayer, and vlc, but right now, I'm going to work on figuring out the best way to capture just the active part of a NTSC input in something like RLE, or huffyuv. hopefully 40 minutes or so on a fast 36GB, and a slow 18GB. I guess my best bet is making a JBOD with all of the 36GB, and only half the 9GB. hopefully that'll be enough.

TeeTylerToe wrote: ok, after further investigation, the O2 works pretty fantastically at capturing uncompressed video. it's more then happy to capture full resolution NTSC to your heart's content.

not only that, it'll encode that captured uncompressed video to mjpeg at just about realtime.

what it absolutely refused unconditionally to do, is play back any kind of uncompressed full frame video at any framerate above 5fps... I should probably try mplayer, and vlc, but right now, I'm going to work on figuring out the best way to capture just the active part of a NTSC input in something like RLE, or huffyuv. hopefully 40 minutes or so on a fast 36GB, and a slow 18GB. I guess my best bet is making a JBOD with all of the 36GB, and only half the 9GB. hopefully that'll be enough.

I'm not terribly familar with NTSC but uncompressed PAL is usually 20-25Mb a second. The O2's internal SCSI is something like 20Mb/s, and is shared for all internal disks. The O2 was designed for real time recording and playback of compressed video - using specific formats that can be streamed through the ICE for hardware assistance.

In fact, I just had a look in SGI's sales manual, and it specifically says that the O2 can do real time playback of qt/mv/avi at 30fps only if the video is JPEG encoded. For recording, it says uncompressed capture requires a suitable external disk array (but these comments were based on the lowest possible R5k/R10k CPU configurations, and probably older disk technology).

it's about 17.5 megabytes a second. the Ultra wide SCSI-2 that the O2 uses is 16 bit, 20MHz iirc, I'm sure it's 40MB/s.

With no audio, or audio at 22KHz 8 bit mono no frames dropped, 32KHz 8bit stereo I think frames started dropping >.<. looks like 250MHz is a stretch. I can record the audio seperately I guess.

TeeTylerToe wrote: it's about 17.5 megabytes a second. the Ultra wide SCSI-2 that the O2 uses is 16 bit, 20MHz iirc, I'm sure it's 40MB/s.

With no audio, or audio at 22KHz 8 bit mono no frames dropped, 32KHz 8bit stereo I think frames started dropping >.<. looks like 250MHz is a stretch. I can record the audio seperately I guess.

Yes the O2 SCSI is 40MB/sec.

Here is some benchmarks made with my O2 and differnt disks.
30MB/s possible with modern disk on sequential writes.

ok, I've got 50+ GB of hdd space, hopefully more friday. I'll look into working with avcapture. I was getting minimal framedropping with no audio, and xvm (with abort on framedrop it ran for almost a minute).

what advice doe people have on recording uncompressed? 720x486? the default is 640x480. should I use quicktime, or .mv? interlaced? 422 rather then apple24, or what not?

also, I haven't figured out how to do two things. record directly to the file, and how to pause without invoking the processing, which takes too long for a commercial break, which is why I'm looking at avcapture again.

right now, I'm looking at quicktime container, hoping it'll be more cross platform, 422 because it's 2bpp rather then anything that's 24 bit or more, 640x480 because it's the default full res ntsc for mediaplayer.

has anyone used mplayer or vlc to record from an O2?

Thanks. I'll try and write up something with some tips and with the helpful info people have posted.

I've got a 36GB 10K drive off the external, and a narrow 18GB where the CD drive would normally be. I made a slice at the end of the 36 that's exactly the size of the 18GB, I striped that with the 18GB then concatted that with what was left of the 36 getting about 10000000 blocks or something.

I tried to record about 20 minutes of house last night unattended, got an error.

TeeTylerToe wrote: what advice doe people have on recording uncompressed? 720x486? the default is 640x480. should I use quicktime, or .mv? interlaced? 422 rather then apple24, or what not?

If I recall, you should record NTSC at 640x480 or PAL at 720x512. There may be a spec you see that shows more "lines" for NTSC, etc, but that's to accommodate overscan in the signal, you don't need to digitize it. If someone wants to pipe in otherwise, they may actually have experience - I'm just going from reading. Note that NTSC and PAL have aprox. the same bandwidth, the higher res in PAL is offset by a lower field rate.