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Songcast sync on Raspberry Pi
13-01-2016, 09:42 PM
Post: #1
Songcast sync on Raspberry Pi
Hi,

Is it possible to improve the songcast synchronization between OhPlayer and other receivers/senders? Would adding a real-time clock improve in this case? If so, what specs would be appropriate?

Thanks.
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13-01-2016, 10:33 PM
Post: #2
RE: Songcast sync on Raspberry Pi
Hi Latka,

The implementation currently assumes a reliable network for initial synchronised start, and a sender with access to an accurate clock which timestamps packets as close to the wire as possible. If you cannot guarantee a reliable network (for example if you're using wireless/powerline), you would need to write additional code to make sure your receivers start in sync.

In order to maintain good synchronisation between receivers/senders you would need a reliable high precision clock capable of supporting the Songcast spec (assuming an MCLK that is 256 * 44K1, or 256 * 48K). Sync is possible to half that rate. OpenHome provides a clock-pulling architecture to allow integrators to ensure that senders/receivers maintain sync.
You can read more about the Songcast spec at: http://wiki.openhome.org/wiki/Av:Developer:Songcast:Ohm
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14-01-2016, 10:30 AM
Post: #3
RE: Songcast sync on Raspberry Pi
(13-01-2016 09:42 PM)Latka Wrote:  Hi,

Is it possible to improve the songcast synchronization between OhPlayer and other receivers/senders? Would adding a real-time clock improve in this case? If so, what specs would be appropriate?

Thanks.

Hi Latka,

On my Java version of MediaPlayer we found that fitting this:

http://cpc.farnell.com/piface/shim-rtc/r...dp/SC13528

helped with Songcast synchronisation.

Not sure how successful it would be on the OpenHome ohMediaPlayer, but for £9 it might be worth trying.

Thanks,

Pete.
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31-01-2016, 09:40 AM
Post: #4
RE: Songcast sync on Raspberry Pi
Just wondering: something like that wouldn't be enough: http://www.aliexpress.com/item/DS3231-Me...37540ef7e2 ?

Seems a bit cheaper than 9GBP, so you could both have it and grab a pint or two.
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16-02-2016, 03:52 PM
Post: #5
RE: Songcast sync on Raspberry Pi
I have had poor songcast sync between my PC and the piplayer, could start playback maybe 0,5 s late, and soon be 1-3 s late (different from time to time), practically impossible to use for movies...

The network is a wired 1000 Mbit/s, except the 100 Bbit/s link to the raspi.

But after I have setup one raspi as a local ntp-server on my lan and then sync all other computers against that with a short interval it seem to be much better syncing.

Have not test it for a long time, but now the playback seem starting in acceptable sync for a movie. After a while it could be a little delay, but not more than some 0,1 seconds!

Dont know if it is tecnically possibly that this could improve the syncing, but it seems doing it.
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02-02-2018, 06:37 PM
Post: #6
RE: Songcast sync on Raspberry Pi
Hello

I have just installed an RTC on my raspberry pi running ohplayer and it seems to have fixed the synchronisation issues. I have testing casting from a DSM to the pi and from the pi to a DSM and I cannot hear any delay which is really great.
I used a similar clock to https://thepihut.com/products/mini-rtc-m...spberry-pi. I am using an IQAudio Dac+.
The delay before was always very noticeable when walking from one room to the other.

Really happySmile
Martin
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