1 2 3 Previous Next 41 Replies Latest reply: Oct 3, 2009 6:30 AM by Winston Churchill
Liu Wenjie2 Level 1 Level 1 (0 points)
I have some 720P HD Movies (3584K bps), I put these movies in my xp(sp3) machine, I use iTunes 9.0.1 streaming to my appletv(Ver 2.4) with 100M ethernet connection. Appletv can play these movies, but it like to buffer for every 8~10 minutes. I don't know the reason or method to solve this problem.

Thanks for your help.

Macbook, Mac OS X (10.6)
  • 1. Re: Buffer, and buffer...
    capaho Level 4 Level 4 (3,650 points)
    I have the same problem when attempting to stream large video files from my iMac to my ATV, it just doesn't seem to have the capacity for streaming large files. I finally gave up and bought a Buffalo Link Theater to use for streaming video from my computer or network drive to my TV.

    One thing you could try would be to start the movie, then pause it and wait a few minutes to give it time to cache far enough ahead so that it doesn't pause so frequently while playing. However, you'd probably be better off syncing your movies first and playing them from the ATV hard drive rather than trying to stream them.
  • 2. Re: Buffer, and buffer...
    Winston Churchill Level 10 Level 10 (81,985 points)
    How many chapters does the video have.
  • 3. Re: Buffer, and buffer...
    Alley_Cat Level 6 Level 6 (17,040 points)
    Could the drive the movie streams from be powering down every so often - say the AppleTV buffers 10% of the movie quite quickly, then it may not fetch more data until this bufer is almost empty, by which time the distant drive has gone into a power saving state.

    This may not be the case, but several of my external drives are 'green' by design which mean they spin down after a couple of minutes of inactivity.
  • 4. Re: Buffer, and buffer...
    Alley_Cat Level 6 Level 6 (17,040 points)
    I don't think anyone here knows for sure how AppleTV buffers streamed files - is it to a small RAM buffer (it only has 256 MB in total to start with), small buffer on internal drive, whole file to internal drive, combination of RAM and drive buffer etc etc, and even then what happens may vary depending on remaining capacity on the AppleTV.

    If it buffers in chunks say 5-10% then on a fast network this buffer will fill quickly - if AppleTV doesn't maintain the buffer size, but just fetches the next 5-10% when the buffer is nearly empty it could result in problems due to rebuffering at regular intervals when remote drives spin down and take a few secs to spin up.

    A slow connection would probably struggle to fill the buffer quickly, and the drive would be constantly accessed and not have time to spin down.
  • 5. Re: Buffer, and buffer...
    Liu Wenjie2 Level 1 Level 1 (0 points)
    Only one chapter for every movie
  • 6. Re: Buffer, and buffer...
    capaho Level 4 Level 4 (3,650 points)
    I don't think anyone here knows for sure how AppleTV buffers streamed files....


    I did a bit of experimenting with mine because of my own frustrations with choppy streaming, and it appears to me that it writes ahead to the disk cache, assuming there is enough space. It's easy to test this hypothesis, as I alluded to previously. If you start a stream and then pause it, the longer it is paused the longer it will play without interruption. That would not be possible if it were caching just to memory, it would have to be using the disk cache.
  • 7. Re: Buffer, and buffer...
    Winston Churchill Level 10 Level 10 (81,985 points)
    You might find that having more chapters might solve your problem. The tv is always trying to read the chapter it is writing when there is only one chapter.
  • 8. Re: Buffer, and buffer...
    capaho Level 4 Level 4 (3,650 points)
    The tv is always trying to read the chapter it is writing when there is only one chapter.


    Exactly what does that mean?
  • 9. Re: Buffer, and buffer...
    Winston Churchill Level 10 Level 10 (81,985 points)
    capaho wrote:
    The tv is always trying to read the chapter it is writing when there is only one chapter.


    Exactly what does that mean?


    It means, the tv is always trying to read the chapter it is writing when there is only one chapter.

    I noticed from an early stage that videos with one chapter sometimes do not perform too well. It's not always noticeable but it's more noticeable when you try rewinding than it is when its playing. A video will rewind much more smoothly when it's rewinding a chapter it isn't downloading. If the tv is reading and writing the same chapter at the same time things can get a little glitchy.

    Note I'm referring to a video that has one chapter not a video that has none, which is handled differently.
  • 10. Re: Buffer, and buffer...
    Liu Wenjie2 Level 1 Level 1 (0 points)
    "Note I'm referring to a video that has one chapter not a video that has none, which is handled differently."


    Do you explain appletv to handle a video that has none chapter?
  • 11. Re: Buffer, and buffer...
    capaho Level 4 Level 4 (3,650 points)
    It means, the tv is always trying to read the chapter it is writing when there is only one chapter.


    Sorry, but that still doesn't make any sense to me. What specifically do you mean by "reading the chapter it is writing," as in reading from where and writing to where?
  • 12. Re: Buffer, and buffer...
    capaho Level 4 Level 4 (3,650 points)
    Do you explain appletv to handle a video that has none chapter?


    His answer doesn't make much sense to me either, but I think he may be trying to say that he believes there is a bug in the ATV software that manifests itself if a video has only one chapter. If that's the case, then a workaround might be to make sure the video has either no chapters or at least two chapters.
  • 13. Re: Buffer, and buffer...
    Winston Churchill Level 10 Level 10 (81,985 points)
    Liu Wenjie wrote:
    "Note I'm referring to a video that has one chapter not a video that has none, which is handled differently."


    Do you explain appletv to handle a video that has none chapter?


    If a video has chapters, it is divided up into those chapters and you are able to advance from one chapter to the next in a similar way to a DVD.

    If a video has no chapters, the tv divides the video up into 20 equal sections and you are able to advance through the video in the same way as though the video had chapters itself.

    If a video has one chapter the tv does not divide it up and so you cannot advance it as you can when it has multiple or no chapters, if you do it just jumps to the end of the video.

    It is in instances such as the later case that I have found the tv to perform less well especially when it comes to fast forward and reverse but also occasionally during playback. I have put this down to the fact that the stream it is receiving and writing to its drive is always part of the same chapter it is trying to read from its drive and playback.

    As the tv is a closed system it's difficult to know exactly what is happening in there and whether it works the way I think it might or not, the one chapter issue is something that I have noted and tested on more than a few occasions.

    Generally, one chapter movies are a bit of a nightmare anyway even if only for the reason that you can't advance them in the way you can other video, so they are definitely something I would recommend avoiding.
  • 14. Re: Buffer, and buffer...
    capaho Level 4 Level 4 (3,650 points)
    You essentially have it backwards. The data stream is written to the disk cache as it is received and the ATV reads the video data from the cache. If it reaches the end of the cache, the video stalls as the ATV waits for more cached data to be written until it reaches the minimum required to resume playing the video.

    A "chapter" is merely a data marker placed at a specific point. Based on your explanation, you are saying there is a bug in the ATV software that degrades streaming performance if a video file has only one chapter.
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