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AFP performance and remote streaming media playback - Mac Networking

I recently moved the majority of my doents from my desktop machine to a dedicated AFP server running netatalk 2.0a1. In addition to the desktop machine, I have a Powerbook connected via Airport Extreme. Both are running Panther 10.3.2. The following behavior was also observed using one of the MacOS boxes as the AFP server, so it does not appear to be netatalk-specific, however. I'm noticing that when playing back high-bandwidth video files (2-300kbps and up) from an AFP-mounted volume, playback is not smooth. There are occasional hangs and stutters, etc, even though the network medium (802.11g for my laptop, ...

  1. #1

    Default AFP performance and remote streaming media playback

    I recently moved the majority of my doents from my desktop machine to
    a dedicated AFP server running netatalk 2.0a1. In addition to the
    desktop machine, I have a Powerbook connected via Airport Extreme. Both
    are running Panther 10.3.2. The following behavior was also observed
    using one of the MacOS boxes as the AFP server, so it does not appear to
    be netatalk-specific, however.

    I'm noticing that when playing back high-bandwidth video files
    (2-300kbps and up) from an AFP-mounted volume, playback is not smooth.
    There are occasional hangs and stutters, etc, even though the network
    medium (802.11g for my laptop, 10Mbps HPNA from my desktop to my server
    and wireless hub) easily supports needed bandwidth. I'm noticing this
    issue with all three major media player apps (WMP9 for OS X, Quicktime
    Player 6.5, RealOne Player), although Windows Media Player has the most
    severe problems. The higher the file's bandwidth, the more severe the
    playback hiccups.

    I'm presuming that the reason for this is that those applications do not

    read the entire media file when it is opened, and instead stream the
    file off of the mounted volume during playback. Because the apps don't
    know or care that the file is not local, they don't create large enough
    buffers to deal with routine network latency and ethernet collisions,
    and that causes the observed playback issues.

    Is there any way to prevent this, either by enabling some sort of

    client-side file caching in AFPD or by increasing the read buffers in
    the player apps? It appears that the "big three" player apps only offer
    buffering controls when the file is accessed via a streaming network
    protocol such as http or rtsp. Sure enough, if I serve the file over
    http instead of afp, and open the file by entering its URL into the
    player app, the file plays smoothly; the app is aware of the network
    transport and creates an appropriate-sized preload buffer to ensure
    smooth playback.

    Any suggestions would be appreciated.

    Thanks,



    -Chris
    Chris Guest

  2. #2

    Default Re: AFP performance and remote streaming media playback

    On Sat, 06 Mar 2004 11:14:56 -0500,
    Chris Woodfield (net) wrote: 

    netatalk-2.0a1 is _alpha_ code as the release name indicates. You could
    try posting this to sourceforge.net to bring it to
    the attention of netatalk developers.

    I know you did post it to netatalk-admins, because I read your message
    there about 2 months ago.

    I know this is not a generic problem with all AFP3.1 implementations.

    --
    Bev A. Kupf
    "The lyfe so short, the craft so long to lerne" -- Chaucer
    Stripes - Martha Stewart's new Spring collection
    Bev Guest

  3. #3

    Default Re: AFP performance and remote streaming media playback

    Reread my first paragraph; I updated my original post to the
    netatalk-admins list to mention that I'm also seeing this problem when
    playing a file from my desktop Mac to my Powerbook and back, not only
    when playing a file from the netatalk volume. I kept most of the post
    because the particulars did not change, but the fact that I observed
    this outside of netatalk warranted a wider audience, IMO.

    I just finished another test where I connected the Powerbook via wired
    ethernet to the 100M switch my desktop connects to; this played back
    with no problems. So it does appear to be an issue with network latency
    and collisions which are endemic to 802.11g and half-duplex ethernet.
    Larger read buffers in the apps are the obvious fix, IMO...

    Bev A. Kupf wrote:
     
    >
    >
    > netatalk-2.0a1 is _alpha_ code as the release name indicates. You could
    > try posting this to sourceforge.net to bring it to
    > the attention of netatalk developers.
    >
    > I know you did post it to netatalk-admins, because I read your message
    > there about 2 months ago.
    >
    > I know this is not a generic problem with all AFP3.1 implementations.
    >[/ref]
    Chris Guest

  4. #4

    Default Re: AFP performance and remote streaming media playback

    On Sat, 06 Mar 2004 12:31:10 -0500,
    Chris Woodfield (net) wrote: 

    I do not observe this playing mp3 files over either a 10baseT network
    or a 100baseT using 10.3.2 as an AFP server or EtherShare 3.1

    Haven't experimented with netatalk-2.0a yet, but a similar Linux PC
    with netatalk 1.6.4 doesn't have a problem when the share is mounted
    as AFPoverTCP, only when it is mounted as a DDP share.

    --
    Bev A. Kupf
    "The lyfe so short, the craft so long to lerne" -- Chaucer
    Stripes - Martha Stewart's new Spring collection
    Bev Guest

  5. #5

    Default Re: AFP performance and remote streaming media playback

    Bev A. Kupf wrote: 
    >
    >
    > I do not observe this playing mp3 files over either a 10baseT network
    > or a 100baseT using 10.3.2 as an AFP server or EtherShare 3.1
    >
    > Haven't experimented with netatalk-2.0a yet, but a similar Linux PC
    > with netatalk 1.6.4 doesn't have a problem when the share is mounted
    > as AFPoverTCP, only when it is mounted as a DDP share.
    >[/ref]

    mp3s and other audio formats are fine; the problem is with
    high-bandwidth video files in the 500kpbs and up range. Quicktime Player
    seems to be the least troubled, Realplayer files are a bit worse.
    Windows Media files are horrible - one 800kbps .asf file I have is
    completely unplayable across a half-duplex ethernet network.

    I'm suspecting this is more of an application issue than a problem with
    AFP itself; At least this thread will make the issue known if there's no
    way to correct this in the OS (Hey MSMBU, you paying attention?)

    IMO, the best way to fix this issue would be for the application to be
    aware (if possible) when it is reading a file from a network volume as
    opposed to a local disk, and if so, increase the pre-buffer cache size
    to suit. If that is too difficult, having the pre-buffer preference
    field (all three apps have one) affect file streaming buffering as well
    as network streaming would be a suitable fix as well.

    -C
    Chris Guest

  6. #6

    Default Re: AFP performance and remote streaming media playback

    In article <semihuman.com>,
    Chris Woodfield <net> wrote:
     

    The performance of 802.11g is terrible. The bandwidth drops off very
    rapidly with distance and it's using an RF band crowded with cordless
    phones, walkie-talkies, gadgets, and microwave ovens. It's very
    convenient but your wireless AFP server will never be mistaken for a
    local hard drive.
    Kevin Guest

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