PDA

View Full Version : Can't stream movie.




macphin
Apr 3, 2007, 05:55 AM
Hi there,

Got my apple tv yesterday, have still some questions.

I've had some movies that were .mkv but I've reencode them into .mp4. They're HD 720p. And these movies couldn't stream. Apple TV found them but when I'm trying to play them, he's just trying to stream, but play nothing. That's not the deal, because, apple tv streaming my HD 720p trailers from mac, just fine. If I sync them directly to apple tv, everything is allright. But I just couldn't stream them. My networg is 802.11g, but still, I can stream all of my DVD(mp4) movies and 720p trailers. Why do I bother? Because the size of one movie is about 6gb... it tooks quite long to sync it.


And actually I'm not sure whether Airport Extreme 802.11n will help in this case.

Here are the movie info:

Data rate: 6941.41 kbits/sec
FPS 23.98
Size: 1280x544

Here (for example) movie info from apple 720p trailer (streams fine):

Data rate: 6189.69 kbit/sec
FPS: 23.98
Size: 1280x544



Also, if I'm syncing a movie and disturb it, just easily trying to play it on apple tv, the syncing is automatically cancelled, and, I'm losing all date that has been synced already. Do you have the same? Check it.



KershMan
Apr 3, 2007, 05:59 AM
This movie is well past the data rate that works synching over a g network. You are talking almost 7 MBps. That is huge and past the performance of a G network. That would be 56 Mbps, and g has a max rating of 54 Mbps, but really only does about 24-27 depending on network connections (range, interference, etc.).

You will have to make this file smaller (IE, throttle back the data rate) or upgrade to n. I haven't done the research on n, but I would think you could get that throughput.

macphin
Apr 3, 2007, 03:02 PM
Yeah, I almost agree with you, but I still can't get why does the movie trailer (which is about 800kbit/s less than the movie itself) streams just fine.

Avatar74
Apr 6, 2007, 02:02 PM
This movie is well past the data rate that works synching over a g network. You are talking almost 7 MBps. That is huge and past the performance of a G network. That would be 56 Mbps, and g has a max rating of 54 Mbps, but really only does about 24-27 depending on network connections (range, interference, etc.).

You will have to make this file smaller (IE, throttle back the data rate) or upgrade to n. I haven't done the research on n, but I would think you could get that throughput.

Actually 6941Kbps is is about 6.78 megabits per second, not megabytes. (kilobits/1000 = megabits; kilobits/8 = kilobytes)

The bigger issue is actually the AVC decoder thresholds. Even if the file is read directly off the local hard drive, files that surpass the stated threshold might play back with errors/artifacts if the sample & hold buffer in the decoder doesn't have enough time to accurately calculate the appropriate values for each pixel in a given frame. Even worse if you have an image that's being upsampled on the fly to scale to the output resolution matched to your display.

Think of it sort of like the episode of I Love Lucy where the chocolates are coming down the conveyor belt. The faster they come the less time there is to inspect each one of them. Same concept with digital sampling... sample & hold times in D/A converters and digital upsamplers are critical to maintaining the accuracy of the output signal relative to the encoded input signal. If sample & hold times are too short, errors will occur and output fidelity will be compromised.