[atv] how to troubleshoot "buffering" for HD content?
#1
I have had a crystal HD card with the latest nightly build and r26 driver for a few months now and everything has been great. For the past week however, every time I try and stream (via SMB share on Win7 via SATA external HDD) a 720p or 1080p movie, XBMC stops in the first minute and has to buffer for 5-10 seconds, and then it continues to pause regularly every 30-90 seconds after that to buffer again, and again, and again... SUPER ANNOYING!

I have wiped my ATV (restored) and re-installed everything. Removed all content being synced from iTunes to ATV. Still get "buffering" message all the time.

Installed Ubuntu and XBMC. still get it.

Tried re-booting Win7 PC. Turned off all Win7 background processes. Replaced ethernet cable from switch to PC. Replaced cable from switch to ATV. Rebooted router/switch.

Nothing has worked so far.

Here is one relevant section of my xbmc.log file (under ubuntu 8.04 on ATV): http://pastebin.com/rugw1W5A
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#2
Is this a 100mbit ethernet network? What is the buffer size of the HDD?
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#3
yeah, i have a linksys wrt610n router/switch that the ATV is plugged directly into, and so is my Win7 box. Win7 box is actually gigabit.

interesting though, I just used winscp from the Win7 box to try and copy a 8gb file over to ATV and it was giving me 2.5MB/sec transfer rate. SLLLLOOOOWWWW!!!! Said it would take 55 minutes to copy the file.

Tried transfering it from my Win7 box (wired) to my Macbook Pro (wifi), and it only took 7 or 8 minutes (about 11MB/sec).

Now copying the same file from my MBP over wifi to my ATV (wired) via Fugu and it's getting 10.6MB/sec.

I am wondering if my router has bit the dust and is causing the bottleneck on transfers from one ethernet port to another.
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#4
Defrag your hard drives!
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#5
just checked, and all my drives are 0% fragmented. just ran automatic weekly scheduled defrag last night in fact.

to help clarify the situation further, i have found that:

- if i copy a x264 720p/1080p movie to my macbook pro and share it via SMB over Wifi, it plays fine in XBMC on ATVOS or Ubuntu
- i can copy from win7 (gigabit) to macbook pro (wifi) and from there to my ATV (100baseT) all at around 11MB/sec.
- 1080p and 720p play perfectly when played from ATV hard drive

the problem only exists when streaming from Win7 SMB (gigabit wired) to ATV (100baseT), or copying, both have a transfer rate of only 2.5MB/sec.

next i am going to turn off wifi on my MBP and wire it into my switch in place of my Win7 server and see what happens. i have already tried changing ethernet cables, resetting the wrt610n router/switch.
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#6
You must have high bitrate content then. You say you only get 2.5MB streaming, but that's two and a half megabytes. That equates to a 20mbit video bitrate. Seems like OK throughput to me. 2.5MB over SSH to aTV is normal, if you want a faster xfer install FTP.

Your having issues with drive transfer? Is your drive in PIO mode?

Personally, I would check network latency. Ping the aTV from different nodes and check performance.
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#7
so i fixed it for XBMC under ATVOS:

http://superuser.com/questions/142524/di...operations
http://blog.djmnet.org/2009/02/09/macs-n...k-geekery/

created /etc/sysctl.conf
added these lines:

net.inet.tcp.delayed_ack=0
net.inet.tcp.mssdflt=1440
kern.ipc.maxsockbuf=500000
net.inet.tcp.sendspace=250000
net.inet.tcp.recvspace=250000

I have the initial 5-10 seconds of stutter at the beginning of 720p content, but no more buffering errors.

But I am still having problems in XBMC under Ubuntu. It literally stops to buffer every minute or two... ARRRRGGGGhhh....
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#8
Sam.Nazarko Wrote:You must have high bitrate content then. You say you only get 2.5MB streaming, but that's two and a half megabytes. That equates to a 20mbit video bitrate. Seems like OK throughput to me. 2.5MB over SSH to aTV is normal, if you want a faster xfer install FTP.

Your having issues with drive transfer? Is your drive in PIO mode?

Personally, I would check network latency. Ping the aTV from different nodes and check performance.

i did a ping test from Win7 box to ATV and everything came back in less than 1 ms. pinged from ATV to Win7 and it was the same. pinged from MacBookPro (over wifi) to ATV and also all less than 1ms.

it's not content that has too high of a bit rate for the ATV to play. these are the same movies and shows I've watched for ever and ever on my ATV (since I got the Crystal HD chip installed), and they have always worked fine.

Now for some reason, I can't seem to get a good data transfer rate from my Win 7 SMB share to the ATV over my Linksys WRT610N.

i wonder if a recent windows 7 update had anything to do with it.
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#9
trevorcobb Wrote:so i fixed it for XBMC under ATVOS:

http://superuser.com/questions/142524/di...operations
http://blog.djmnet.org/2009/02/09/macs-n...k-geekery/

created /etc/sysctl.conf
added these lines:

net.inet.tcp.delayed_ack=0
net.inet.tcp.mssdflt=1440
kern.ipc.maxsockbuf=500000
net.inet.tcp.sendspace=250000
net.inet.tcp.recvspace=250000

I have the initial 5-10 seconds of stutter at the beginning of 720p content, but no more buffering errors.

But I am still having problems in XBMC under Ubuntu. It literally stops to buffer every minute or two... ARRRRGGGGhhh....

nevermind, this was just a bandaid, didn't fix the real issue.
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#10
just wanted to update you guys, that I followed the instructions in these links, and I can see now that FTP is *WAY* faster than SFTP or SCP for transfering to/from the ATV. I don't really have a way to test my samba speeds, but my buffering issues with HD content went away with a new nightly build several weeks ago.

http://devroot.org/2007/05/01/optimize-n...r-appletv/
http://wiki.awkwardtv.org/wiki/Enable_FTP_Server
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#11
I'm having the same problem after I updated xbmc to latest svn and crystal hd driver to r143 using deltazulu's method (http://forum.xbmc.org/showthread.php?tid=74992&page=67). I'm using pin87a usb image.
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[atv] how to troubleshoot "buffering" for HD content?0