Readahead for HD Video Playback CIFS/NFS/FTP over Wi-Fi

[erdem_ua]

802.11n dongles will cure that problem which appears with 16GB streams, right?

[wannaseek]

N dongle will fix it very likely. Strange that the built-in DLNA client can play 16 GB HD movies with g wifi.

Maybe N dongle would even work over CIFS or over NFS transport using the readahead shim. I do not have N dongle.
Someone else can test it when I fixed major issues in the readahead. Btw. as always I have limited time for this, so if you need the solution earlier, please feel free to contribute...

[mattberlin]

Hey guys,

I'm not getting it, why a N dongle would work. As arris69 stated cifs as a 25 MBit limitations respectivly a 12 MBit limiations when using Wifi.
When using the readahead feature you are basciscally reducing the data rate peaks. On the other hands this means that the average Bitrate can never be above those 12 MBit when using wifi.
Am I right?

How does one actually implement the readahead feature?

Best regards
Matthias

[wannaseek]

Matthias,

readahead is not only handles the data rate peaks but also reducing the latency of wifi. According to my tests, reducing the latency is the key in eliminating lagging.

I am not sure that the bandwith limit is 25 MBit over N wifi with CIFS. But if it is really the case, use ftp.

In the meantime I have found the optimal buffer size. I will upload the current version into the svn. But I still have to implement a mechanism to handle seeking properly (cancel background readahead when seeking and detect sequential read before starting readahead). This will take some time.

[mattberlin]

Thank's!
Well, I'm gonna get N anyway.
However, it sounds very interesting what you are doing. I just hope, it won't be to hard to get it run for amateurs like me.

[wannaseek]

I have spent some time on the weekend with fixing major issues with my readaheadfs.

New features:

• readahead is starting after a certain amount of sequential read is detected, can be set by the readahead_start parameter in KByte
• readahead aio is done in a callback chain
• the total size of readahead can be set by the readahead_size parameter in MByte
• size of readahead chunks can be set by the readahead_chunk parameter in KByte. This is the read size which is cannot be cancelled after started

The tool is now in a pretty good shape. I can play/seek many HD videos:
Known issues:

• after stopping a playback, the readahead gets into an inconsistent state, however it does not influence the user experience
• sometime the readahead does not start. You have to press pause, wait, press play, sometimes press rwd 2-3 times, and it always helps.
• directory listing of mp3s are not supported (reading ID3 tags confuses the readahead)
• CPU consumption is higher than expected but OK

I have also created a script to mount curlftpfs and readaheadfs. Let us see how to use it:
1. Unzip the attached stuff into the folder where you unzipped SamyGO All Extensions
2. Edit the server URL in the SamyGO/etc/init.d/05_05_readahead_ftp.init file
3. Rename the SamyGO/etc/init.d/03_03_nfsmount.init file to *.bak (because I am using the NFS fake USB for readaheadfs mount)
4. Copy stuff to the TV and start it from the content menu

I still have some issues to play movies bigger than 9 MBit/s average bitrate via my g wifi. I think my g wifi equipment is also not the best one...

I would appreciate if someone would test it with N wifi. I am interested in the result and plan to upgrade to N wifi if it helps...
It could also make sense to test the readaheadfs in combination with samba or nfs again.
For the ones who meaures >20 MBits/s over Samba and n wifi the readaheadfs in combination with samba should be a working solution.

[wannaseek]

I can see that the file was downloaded a few times.
Has anyone tested it with N wifi and > 8 GB movies? I would be interested in the result.

[hallodri089]

I test it now. I don't hav so many 1080p movies, but even with them I have somethimes lags playing from samba shares.
By the way, I don't use wifi, I use devolo powerline 200mbit adapters.

First impression:
Workload CPU (SamsungB750):
execdsp: 40%
curlftps: 15%
readaheadfs 5%

Moving forward, then play: movie stocks. I've to pause it a few seconds.
Moving forward too much: movies stops, and it will play the next movie

Up to now I don't have lags anymore: good work

[mattberlin]

Great news, that it seems to work.

Unfortunately, I've never dealt with the SamyGo extensions.
I prefer mounting my samba shares via SamyGO.sh at startup. Is there a way to get the readahead running via SamyGO.sh?

Best regards
Matthias

[wannaseek]

you can start SamyGO Extensions from SamyGO.sh by this command:
/mtd_tlib/GGames/SamyGO/rcSGO

It is quite well documented how to install SamyGO Extension. So it is easier to use that instead of copying manually the different libraries and tools to the TV.