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audio video sync at dm36x (IPNC)

Sungil Kim
Intellectual 265 points

Hi everyone

 

I test AV sync at DM365

but there are mis sync problem.

 

I found that audio time stamp / video time stamp and system timestamp is all mismatch

 

test method is here

1. Audio time : sampling rate is 8Khz (ADC is tlv23ac), sample size 1024 (so 7.825 time capure at every 1sec)

             a.  I add  audio time stamp to  11520 (90000 tick)

             b. I get time by gettimeofday and convert to mili second

             c. I caculate (a - b *90) as time goes

              d. result is  400 mili differ at 1 day

               (this time , just audio capture, not video capture, video display, audio encoding )

 

2. System time : I just use ntpclient

                   result is 2 sec differ at 1 day (not use RTC)

                (this time , no audio/video capture, no  encoding, not use RTC)

 

3. Video time : same method use (10 fps)

             a.  I add  video time stamp to  9000 (90000 tick)

             b. I get time by gettimeofday and convert to mili second

             c. I caculate (a - b *90) as time goes

              d. result is  4000 mili differ at 1 day

 

more strange is that  difference is depend on system status (specialy DMA copy)

If dma copy is used (for video out) . difference is more(about 10 times) happend.

 

anyone help me ?  or how to av sync ?

  • 0
    TI__Genius 11000 points

    Can you please tell us which version of IPNC are you using?

    We had some issues with it in version 1.0 but later it was fixed in ver1.5 onwards.

    However, can you check at your end if the sampling rate and RTC is working fine.

    Are you running this on IPNC hardware or on EVM?

     

    Regards,

     

    Raghu

     

     

    Sungil Kim said:

    Hi everyone

     

    I test AV sync at DM365

    but there are mis sync problem.

     

    I found that audio time stamp / video time stamp and system timestamp is all mismatch

     

    test method is here

    1. Audio time : sampling rate is 8Khz (ADC is tlv23ac), sample size 1024 (so 7.825 time capure at every 1sec)

                 a.  I add  audio time stamp to  11520 (90000 tick)

                 b. I get time by gettimeofday and convert to mili second

                 c. I caculate (a - b *90) as time goes

                  d. result is  400 mili differ at 1 day

                   (this time , just audio capture, not video capture, video display, audio encoding )

     

    2. System time : I just use ntpclient

                       result is 2 sec differ at 1 day (not use RTC)

                    (this time , no audio/video capture, no  encoding, not use RTC)

     

    3. Video time : same method use (10 fps)

                 a.  I add  video time stamp to  9000 (90000 tick)

                 b. I get time by gettimeofday and convert to mili second

                 c. I caculate (a - b *90) as time goes

                  d. result is  4000 mili differ at 1 day

     

    more strange is that  difference is depend on system status (specialy DMA copy)

    If dma copy is used (for video out) . difference is more(about 10 times) happend.

     

    anyone help me ?  or how to av sync ?

     

  • 0 in reply to Raghu Kudva
    Intellectual 265 points

    Version of IPNC is 1.0

    I will test 1.5 (anyone heard news of version 2.0 ?)

    I hope that 1.5 version  will solve problem of dma

    Hardware is IPNC and  I think this have not realation about RTC

    (RTC  was used one at booting. is it ?)

    Anyway I sync video time to audio time.  it's good

    thank you Raghu Kudva

  • 0 in reply to Sungil Kim
    TI__Genius 11000 points

    Hi,

    Regarding to the audio video sync issue, i think all experiment you did is very depend on hardware clock (audio/arm/video). But the clock of hardware may have residuals. So when the system runs longer on time, the residuals should become larger.

    can you use RTC to get the timestamp. Because the time stamp is very important on AV Sync. And about the AV sync , you could refer "5.2 Audio/Video Synchronization" on "Application_DesignGuide_IPNC_DM365.pdf"

     

    Regards,

     

    Raghu

     

  • 0 in reply to Raghu Kudva
    Intellectual 265 points

    Problem of DMA is solved by your answer

    I used 1.5 Version of IPNC  ant test that

    It' work good

     

    thank you