Audio and video bitrates? What do you use?

Angelo · 02-16-03, 01:13 AM

What settings do you use for audio and video bitrates? For those of you who followed the Pocket Matrix Guide, have you experimented with these settings? Does it make a noticeable difference in quality when you move up to 250 or higher video bitrates? What is the difference in file size?

geezer · 02-16-03, 04:55 AM

250-300 seems to be the sweet spot. From what I've seen around here, file size of 1.5 to 2 Mb/minute is nominal.

Snipped from the PMVP Help file:

Quote:

So now we know several things about choosing the bit rate.
1) there is a maximum video bit rate for which we can't see any difference in video quality (300 -450 kbps)
2) there is a maximum video bit rate that the PDA can handle (usually less than the preceding maximum.
3) the maxium video bit rate decreases with audio bit rates. (stereo has the biggest impact)
4) Time spent distributing these bits between frames will often have more payback than time spent trying to find the maximum video bit rate.
5) The addition of small amounts of smoothing or the introduction of noise can increase the compressibility of the film, thereby providing more bits which can be used elsewhere for the more demanding frames.

Angelo · 02-16-03, 12:03 PM

Man, if only I had my Axim...

I'm really no expert in this stuff but I interpret those instructions as follows:
1) 450 will be the same as 300
2) the PDA can't even handle 450 anyway
3) if the audio is stereo, then video should be lower than 300
4) ???
5) ???

What do the last two mean?

What are the consequences for choosing bitrates that are too high? Is it just a matter of file size? Or will it not play smoothly, if at all?

scottmso · 02-16-03, 10:30 PM

I encode some of my Simpsons episodes to about 110Kbps/sec Divx 5.0.2 (1-pass) video, frames decimate by 3 (about 8-10 fps), 240x180. The audio is 24kbps MP3 22050Hz. Brings episodes (20mins) down to about 24MB per episode. Not the best quality, but my biggest memory card for right now is a 28MB MMC. I will go up to full 320x240 whenever I get a bigger memory card soon and tell you what settings I use for that.

geezer · 02-17-03, 03:46 AM

Angelo,

I too am no expert. Have you looked at the PocketMVP help file?

My interpertation of #4 and #5:

4 - The Axim is only capable of so much. The beauty of Virtualdub and PocketMVP is the ability to adjust your audio/video settings to your personal preference - within reason!

5 - I've read reports of various gains/losses when using the MANY filters available with Vdub. A look through Nicky's pages will be worth your time.

Nicky's Digital Guides

Quote:

What are the consequences for choosing bitrates that are too high? Is it just a matter of file size? Or will it not play smoothly, if at all?

Ah, you will probably become very familiar with the reset button on your Axim when tweaking your video files...:)

Angelo · 02-17-03, 12:58 PM

scottmso,
Wow, is it even watchable with those settings? Nevertheless, its amazing that 30 minutes of video can fit on such a small MMC. But memory is getting cheap now!

How did you get the Simpsons (or anything from TV) on the computer? From a DVD? Does your video card have a A/V Inputs?

Quote:

Ah, you will probably become very familiar with the reset button on your Axim when tweaking your video files...

So in other words, its a lot like the other versions of Windows? Is the soft reset like CTRL+ALT+DEL? Is there a blue screen or does it just lock up?

I've been encoding my short movies (Austin Powers, Rush Hour, animated movies) with different settings to experiment. When I've found the "optimal" settings I'll go ahead and do the long movies. (Crouching Tiger, Matrix, Star Wars series)

I hope the "optimal" settings don't differ from movie to movie.

chuck12 · 02-17-03, 05:25 PM

I use the defaults and they work perfectly fine

geezer · 02-17-03, 06:44 PM

Quote:

? Is there a blue screen or does it just lock up?

I've just seen lockups and blank screens with PMVP when trying bad video files.

Quote:

When I've found the "optimal" settings...

I hope your luck is better than mine. I used identical setting from a successful compression for a file from another format (DVD vs. Hi-8 tape) and it crashed the Axim. A/V sync is another headache, depending on your system.

I tape on a Sony Hi-8 camcorder, dump to PC via Dazzle USB converter, capture to .avi with bundled sotware, crunch and massage with Vdub and, finally, copy to CF card via PCMCIA adapter.

I have a Canopus AVDC100 converter (any A/V in to digital out) on the way, which hopefully will eliminate a lot headaches.