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video buffering alot during stream 720p Video - SMB
#1
Platform: AppleTV2
Build Version Built on Mar 5 2011 (Git:b0b7aa9)


Here is the problem, I stream a 720p ( h.264 video from local server via 100 mb Network ).
And most video will buffer every now and then, down to once a minute, but it seems to be related to bitrates of the encoding.
I am streaming via SMB protocol from a Ubuntu file server.

So I did some test. Being an cisco network engineer, I wanted to see what was happening on the network. So I did the following test.

Played a movie both on a Atv2 and on a Media PC (running ubuntu and xbmc ) here are the specs for the movie.

Type:Video
Codec: H254 - MPEG-4 AVC
Res 1280x536
Framerate 23.976215

Type Audio
CodecBig GrinTS audio(dts)
Channels: 3f2r/LFE
Sample rate:48000 hz
Bitrate1536 kb/s


I played the first 3 min of the movie, on both PC and ATV2.

Pc specs are 100mb network, HDMI out, Audio via HDMI to TV (same as ATV2)

on these 3 min the ATV2 Buffered 4 times ( meaning the video stopped the buffering started to count up ) and then continued.
on the pc no buffering happened at all.

I did a network graph of both the stream an you can see that the Ubuntu box is taking more bandwidth... when watching the movie about 50kb more.
Here are the graphs.
Apple TV 2
Image

PC
Image


Here is also the xbmc.log
The Atv2 is not doing thumbnails in the background since I have my thumbs on an smb and lib database is on central mySql.
Both machines where not scanning for new content while playing the movie.

So I wonder if this is due to audio problems of the video or if its the smb client on the atv2 that is haveing some issues, since I read here in forums ppl solving problems by using ftp.
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#2
Interesting... to confirm if its audio related it would be needed to pass through the audio to some capable receiver, can you do that?

I'm guessing also its the ATV2 smbclient which can't handle correctly.
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#3
I have tried to change the audio output to Spdif, and it does not change this fact.
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#4
haffi Wrote:I have tried to change the audio output to Spdif, and it does not change this fact.

Am I right in concluding network speed is not an issue here?
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#5
I have a suspicion it's related to the buffer, is the buffer large enough to support extended scenes with high bitrate?

I watched a 30min 1080i TV Cap (1440x1080, h264, ac3, 1.9gb) without a single buffering pause via an SMB share on a Western Digital My Book World Edition, the video averages about 8mbps and peaks at 18+mbps so the hardware is certainly capable of playing such media.

Is the small RAM size of the ATV2 restricting the amount of data that can be buffered?

Update: Heres a screenshot from Bitrate Viewer of the above video clip:

Image

It would probably be good for others experiencing the buffering issues to provide the same sort of screenshots.
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#6
pecinko Wrote:Am I right in concluding network speed is not an issue here?

its possible.. but with the specs of the movie... i doubt that file is larger than 8GB... 100MB ethernet can usually handle at least a 15GB file file over samba
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#7
bircoe Wrote:I have a suspicion it's related to the buffer, is the buffer large enough to support extended scenes with high bitrate?

I watched a 30min 1080i TV Cap (1440x1080, h264, ac3, 1.9gb) without a single buffering pause via an SMB share on a Western Digital My Book World Edition, the video averages about 8mbps and peaks at 18+mbps so the hardware is certainly capable of playing such media.

Is the small RAM size of the ATV2 restricting the amount of data that can be buffered?

Update: Heres a screenshot from Bitrate Viewer of the above video clip:

Image

It would probably be good for others experiencing the buffering issues to provide the same sort of screenshots.


I had similar buffering issues when using SMB shares on my IcyBox NAS, no issues on my ps3 using upnp so tried that instead and bye bye buffering issues on HD content, I can only assume there are issues with the SMB code on the ATV2?
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#8
I had similar problem. I use SMB on Windows 7 over WIFI. 720p seems quite smooth. Some 1080p is better than others. Not sure what the limitation is.

BTW, try to play 1080p clips from youtube. It doesn't have any problem. So it's not related to network(wifi or wired connection). It's not related to CPU/memory? Maybe SMB client?
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#9
I've suspected the buffer as well (not with atv2 hardware but with xbmc implementation). If you have open a bit rate graph while playing a large file, and then press pause, you'll see that the file will stream for a few seconds and then stop. It seems that the buffer can only hold a few seconds at a time. Also when you ssh in and run 'top' (apt-get install top), you can see that while streaming, the cpu is at a third or less and the ram has about 10mb free. I suspect our network hardware isn't an issue, but how fast xbmc is asking for data is. It's not going to get more data than it's capable of holding on to at a time. There is probably more to it than just the buffer, but couldn't we modify how XBMC buffers so we can open things up a bit?
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#10
haffi Wrote:Platform: AppleTV2
Build Version Built on Mar 5 2011 (Git:b0b7aa9)


Here is the problem, I stream a 720p ( h.264 video from local server via 100 mb Network ).
And most video will buffer every now and then, down to once a minute, but it seems to be related to bitrates of the encoding.
I am streaming via SMB protocol from a Ubuntu file server.

So I did some test. Being an cisco network engineer, I wanted to see what was happening on the network. So I did the following test.

Played a movie both on a Atv2 and on a Media PC (running ubuntu and xbmc ) here are the specs for the movie.

Type:Video
Codec: H254 - MPEG-4 AVC
Res 1280x536
Framerate 23.976215

Type Audio
CodecBig GrinTS audio(dts)
Channels: 3f2r/LFE
Sample rate:48000 hz
Bitrate1536 kb/s


I played the first 3 min of the movie, on both PC and ATV2.

Pc specs are 100mb network, HDMI out, Audio via HDMI to TV (same as ATV2)

on these 3 min the ATV2 Buffered 4 times ( meaning the video stopped the buffering started to count up ) and then continued.
on the pc no buffering happened at all.

I did a network graph of both the stream an you can see that the Ubuntu box is taking more bandwidth... when watching the movie about 50kb more.
Here are the graphs.
Apple TV 2
Image

PC
Image


Here is also the xbmc.log
The Atv2 is not doing thumbnails in the background since I have my thumbs on an smb and lib database is on central mySql.
Both machines where not scanning for new content while playing the movie.

So I wonder if this is due to audio problems of the video or if its the smb client on the atv2 that is haveing some issues, since I read here in forums ppl solving problems by using ftp.

I was also having buffering issues via smb, but if I use upnp or ftp, I have no issues at all.
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#11
what do developer have to say about this speculation?
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#12
Ok Folks, I don't believe there is an issue with XBMC's SMB support or any buffer issues.

Last night I ripped my Fifth Element Bluray to an MKV, I have included a full info sheet from mediainfo, I am currently playing this file on 2 Apple TV's plus VLC on my PC at the same time, from the same SMB share hosted on a Western Digital My Book World Edition (1tb NAS) and have nearly reached the end without a single buffering pause.

Image

As you can see this video spends allot of time at or above 12mbps... I guess it's time to look at your setup's rather than blaming XBMC.

Code:
Complete name                    : The Fifth Element (1997).mkv
Format                           : Matroska
File size                        : 7.78 GiB
Duration                         : 2h 5mn
Overall bit rate                 : 8 846 Kbps
Encoded date                     : UTC 2011-03-18 20:37:06
Writing application              : mkvmerge v4.0.0 ('The Stars were mine') built on Jun 18 2010 07:35:17
Writing library                  : libebml v1.0.0 + libmatroska v1.0.0

Video
ID                               : 1
Format                           : AVC
Format/Info                      : Advanced Video Codec
Format profile                   : [email protected]
Format settings, CABAC           : Yes
Format settings, ReFrames        : 3 frames
Codec ID                         : V_MPEG4/ISO/AVC
Duration                         : 2h 5mn
Bit rate mode                    : Variable
Bit rate                         : 8 030 Kbps
Maximum bit rate                 : 40.0 Mbps
Width                            : 1 920 pixels
Height                           : 800 pixels
Display aspect ratio             : 2.40:1
Frame rate                       : 23.976 fps
Color space                      : YUV
Chroma subsampling               : 4:2:0
Bit depth                        : 8 bits
Scan type                        : Progressive
Bits/(Pixel*Frame)               : 0.218
Stream size                      : 7.06 GiB (91%)
Writing library                  : x264 core 59 r818 d4b7d2b
Encoding settings                : cabac=1 / ref=3 / deblock=1:0:0 / analyse=0x3:0x133 / me=umh / subme=6 / brdo=1 / mixed_ref=1 / me_range=16 / chroma_me=1 / trellis=1 / 8x8dct=1 / cqm=0 / deadzone=21,11 / chroma_qp_offset=0 / threads=4 / nr=0 / decimate=1 / mbaff=0 / bframes=3 / b_pyramid=1 / b_adapt=1 / b_bias=0 / direct=3 / wpredb=1 / bime=1 / keyint=250 / keyint_min=25 / scenecut=40(pre) / rc=crf / crf=22.0 / rceq='blurCplx^(1-qComp)' / qcomp=1.00 / qpmin=10 / qpmax=51 / qpstep=4 / ip_ratio=1.40 / pb_ratio=1.30 / aq=2:1.0
Language                         : English

Audio
ID                               : 2
Format                           : AC-3
Format/Info                      : Audio Coding 3
Mode extension                   : CM (complete main)
Codec ID                         : A_AC3
Duration                         : 2h 5mn
Bit rate mode                    : Constant
Bit rate                         : 640 Kbps
Channel(s)                       : 6 channels
Channel positions                : Front: L C R, Side: L R, LFE
Sampling rate                    : 48.0 KHz
Bit depth                        : 16 bits
Compression mode                 : Lossy
Stream size                      : 576 MiB (7%)
Language                         : English
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#13
glad i found this, just put xbmc on atv2 and SMB shares were buffering too much, all hardwired. ftp is much worse for me, i'm using raidenftpd, what are u using for ftp?
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Image
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#14
well, i think the place on the HDD has something to do with it, as on the atv it will buffer in the same spot of the video everytime.

i had a similar problem with my popcorn hour a-110 in my bedroom, i put my c-200 in there and the problem went away though, so that would indicate a streaming problem. maybe its a combination of the 2?
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Image
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#15
prophetizer Wrote:glad i found this, just put xbmc on atv2 and SMB shares were buffering too much, all hardwired. ftp is much worse for me, i'm using raidenftpd, what are u using for ftp?

Try using vsftpd I have an atv running over wifi with a connection that could be described as flaky at best (crappy internet provider router that refuses to co-operate with any other router I try and connect it to), and using samba results in buffering literally every 2 or 3 minutes, while vsftpd lets me watch an 8gb mkv with maybe buffering once or twice in a movie, it's not perfect but its a massive improvement.
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video buffering alot during stream 720p Video - SMB2