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dave s.
real time encoding
on Oct 13, 2006 at 8:55:36 pm

I am looking for a solution to import video from a camera directly into a mac. Does anyone know of any solutions? either software or hardware based. Also do you know if you can change the quality settings and or compression settings while it is being captured? Idealily I would like to capture something and have it be small enough to be posted directly on the web.


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Rich Rubasch
Re: real time encoding
on Oct 14, 2006 at 4:17:18 pm

I did some test with custom capture presets in Final Cut pro on a Macbook Pro. I set up a DV source to H264, and after some trial and error, there is no doubt that encoding from a clip yields way better results. I also tried some MP4 settings. I am getting about 5 megs per 30 seconds or 10 megs a minute, but the video is pretty chunky, compared to a DV clip encoded with even QT player to H264 which I have better control, multi pass etc.

I think bot mac and PCs really lack a prosumer level appliance app that can take various sources and use standard codecs to encode for web.

So I got it to work, but the results were pretty marginal. Good enough for family videos maybe, but not for clients.

More testing...

Rich Rubasch
Tilt Media


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Rich Rubasch
Re: real time encoding
on Oct 14, 2006 at 4:27:25 pm

Fow what it's worth, I got the best overall results (in black and white) when I digitized using the built in iSight camera in the macbook Pro. The file size was around 6 megs for 30 seconds. It was pretty low framerate and the frames smeared quite a bit with motion.

I kicked up the bitrate on both MP4 and H264 and with about 10 megs per 30 seconds the video was still chunky (240 x 180) although the audio was pretty good. A final option might be to upload at the right size for the final web output, along with frame rate, and then encode that clip which might speed up encoding times.

More tests.

Rich Rubasch
Tilt Media


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Rich Rubasch
Re: real time encoding
on Oct 14, 2006 at 4:38:44 pm

Ok, encoded a PJPEG at 320 x 240 at 75% quality....44k stereo audio at 15fps. the 30 second clip was about 20 megs. I opened that in QT Pro and exported to H264 at the same size at 10fps with the quality slider between low and medium...I did ALaw 2:1 audio at 32K best Mono. Clip looked very good and the 30 seconds came in at 1.8 megs. Perfectly acceptable for client viewing.

So, any realtime encoding takes a serious quality hit, probably because encoders work best when they can analyze the clip first, then encode....encoding on the fly it can't do that.

again, if I were Apple, I would take some of the machine control functions of FCP and combine it with a multipass realtime encoder.

But when I think of it, most of the time we are encoding right off the timeline, not from tape based sources. Not always, but most of the time.

So encoding realtime works, b ut not very well, for now, and it is always best to have a clip.

However, on the PC I have gotten excellent results with Windows Media Encoder when digitizing right off tape sources...it can control a DV device and can even to multi pass by caching to the hard drive on the first pass, then encoding from that clip on the second pass....kind of best of both worlds, but it's not real intuitive to set up.

I might load Win XP on my Macbook and load Windows media encoder and give it a go.

Rich Rubasch
Tilt Media


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mark palius
Re: real time encoding
on Oct 17, 2006 at 3:23:24 pm

Rich Rubasch writes:
>a multipass realtime encoder

Using a conventional definition of "realtime", encoding in 1:1 time as a source is fed, aren't multipass and realtime mutually exclusive terms? How would a CODEC begin the 2nd pass until it has the results of the 1st pass? How can it complete the 1st pass until the source has completed injesting? (assuming 2nd pass requires >0 t.)

regards,
/mp


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Charles Simonson
Re: real time encoding
on Oct 17, 2006 at 5:01:04 pm

I think what he means is that for the live signal, each pass is done in real-time. Of course, in order for this to be accurate, the encoder would need to be able to control a deck or its input source and be able to read some sort of accurate timecode to sync the two passes.



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Charles Simonson
Re: real time encoding
on Oct 16, 2006 at 2:30:07 am

Squeeze can take a DV stream and encode it to some formats in RT. For SDI streams, Ingest Engine from Telestream can encode to MPEG-4 and MPEG-2 Iframe only in RT. There are some MPEG-2 encoder cards for the mac that advertise here. But for the most part, you will likely need a PC for RT encoding. Mostly it is due to how capture cards use QT for capturing on a mac and DirectShow (which offers almost infinite more sw options)on the PC.


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