Are there any DSP techniques to temporally synchronize two different or more digital audio signals without timestamp information?
Synchronizing means to agree in time. To synchronize to streams of audio signals one has to add to them a synchronizing symbol.
Only if one is a copy of the other one can align them by cross correlation.
Best wishes
Hello Abdelhalim abdelnaby Zekry, Could you please elaborate on the term "synchronizing symbol". Yes, cross-correlation can be used to align two "Similar" signals. What about the synchronization of multiple different audio signals?
Best Regards,
Khubaib Ahmad
Unless you can identify a 'marker' - some kind of transient that exists in both/all of your source files then this will be very difficult
Read the term "synchronization symbol" is a generalization of the term "time stamp": with some prior knowledge about the method of synchronization, the synchronization symbol need not be a time stamp in the the narrower sense.
(In some streaming application, the synchronization symbol might be just a counter incrementing by 1 for each Frame transmitted: provided that the sampling rates are identical, and further provided that the start of the data acquisition is somehow synchronized, such a counter would suffice to further assert synchronization.)
To be honest: a time stamp of some Kind is on eof the better means to implement synchronization.
The synchronization means to align in time. So, if you have more than one stream then you have to align them in time. To align bit streams you divide them in frames and then add what is called framing bits. The framing bits can be as small as one bit having a logic zero value to affect synchronization in smaller time one increases the sync word up to 8 bits having a sequence of 01010101 as in case of E1 European multiplexing hierarchy. If you want to synchronize the bits in the two sequences you have to make what is called bit synchronization by synchronizing the clocks of the two streams.
So, you have to study the proper timing method for your case.
Best wishes
U. Dreher Actually I am working on real time audio data more like a voip application. And this is the main issue, in Manets I can’t synchronised the clocks using NTP server and acquiring data at same point synchronously is quite difficult.
Thanks alot for help.
BR,
Khubaib
Stuart Cunningham both streams or I can say audio data is in pcm 16-bit. Other than that its just human voice with sampling rate of 8000.
Abdelhalim abdelnaby Zekry could you please suggest some timing algorithms to solve my problem?
Regards,
khubaib
You can try seeing time frame rate transmitted and sampling rate
Mathematically correlate all data and then synchronisation of multiple audio bits
When you describe what are your streams and why you want to synchronize them i can make you a proposal. However, when you work in packet switched network
Then you can follow the synchronization techniques used in it. It is so that the packets are sealed and addressed and numbered such that one can assemble them at the destination.
Best wishes
Abdelhalim abdelnaby Zekry, My streams are PCM 16-bit mono audio data. Programmatically, a byte array of 640 samples i.e (40ms) of data at 8000 sampling rate. It is recorded from an android phone and transmitted to other android smartphone using RTP. I am unable to initialize the communication synchronously. I can't use NTP in Manets as I read research papers that NTP isn't recommended for manets.
Could you please recommend, If there is any research paper that involves time synchronization or audio synchronization using DSP techniques while keeping in mind that audio streams are different from each other?
Also, I tried to synchronize the different techniques like starting individual clocks using a sound wave of the specific frequency. But still, it didn't work well.
Satish Narula could you please elaborate a little more regarding time frame rate?
Dear Khubaib Ahmad , Please refer to this link to get PDF research papers about
Audio synchronization techniques in a digital transmission system: https://urlz.fr/c1JZ
Dear Khubaib Ahmad an exemple to illustrate clocks synchronization problem: Conference Paper Sub-nanosecond Time Synchronization Mechanism for Radio Inte...