Re: [Discuss-gnuradio] [GSoC 17] DAB: updates of the week

[John Ackermann N8UR]

Hi Benny --

As I mentioned in another message, I'm struggling with the RF-audio 
interface now.  Do you have any example code for your suggestion that I 
might play with (in my mind, the idea would be an "audio synchronizer" 
block that would take input at the nominal audio rate and output at the 
actual rate, correcting for clock error to keep the stream flowing 
smoothly).

If a prototype exists, I'd be happy to plug it into my current app to 
see what happens.

John
----

On 06/06/2017 12:02 PM, Benny Alexandar wrote:
> Hi Luca,
>
>
> Nice to see your progress so far. Once you have the
> DAB receiver audio listening in place, I would
> suggest to have an audio synchronization for continuous
> playback without any buffer overflow or under-runs.
>
> DAB+ audio super frame length is 120ms according to DAB+
> standard (ETSI TS 102 563). Each audio super frame is
> carried in five consecutive logical DAB frames.
> Which means 120ms of audio is mapped to 5 DAB frames.
>
> If I add a timestamp at the receiver when the first DAB frame
> sample arrives, I can check the max latency when it comes to
> audio renderer, I mean after buffering to adjust the variable
> decoding time of compressed audio.
>
> t_D = t_A -  t_B ,
> where,
>  t_A = time at audio out
>  t_B = time at input baseband sample.
>  t_D = maximum system delay.
>
> The difficulty is to estimate the slow clock drift correctly
> and separate it from the short-time channel/decoding jitter.
>
> Add a delay to buffer audio at audio out, say  D, which is larger
> than max system delay. Whenever the audio reaches audio out, check the
> delay to separate the clock drift.
>
>      drift = t_D - D
>
> Please let me know if you need any more details.
>
> -ben
>
>
>
>
>
>
>
>
>
>
>
> ------------------------------------------------------------------------
> *From:* Discuss-gnuradio
> <address@hidden> on behalf of
> Moritz Luca Schmid <address@hidden>
> *Sent:* Friday, May 26, 2017 6:19:31 PM
> *To:* GNURadio Discussion List
> *Subject:* [Discuss-gnuradio] [GSoC 17] DAB: updates of the week
>
>
> Hi everyone,
>
> I just published my latest updates of my DAB project in a new blog post
> <https://dabtransceiver.wordpress.com/>.
>
> This week, I created a source block for the Fast Information Channel and
> started to build a reception chain for the Main Service Channel (where
> the audio data is transmitted).
>
> Read more about it in my post.
>
>
> Cheers
>
> Luca
>
>
>
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