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DM365 Audio Channel Swap

Curtis4590
Prodigy 90 points

 

When playing back dm365 encoded streams on a PC using VLC, the audio is always present, but after a start-up and encoding  the playback of the encoded stream is not always heard on the same channel as a previous recording. As noted in the forum post http://e2e.ti.com/support/dsp/davinci_digital_media_processors/f/100/p/7650/30333.aspx#30333, the audio is sometimes heard on the left channel or sometimes on the right. 

The above forum post refers to McBSP Channel Swapping,  http://wiki.davincidsp.com/index.php?title=McBSP_Channel_Swapping which discusses Start-up and run-time channel swapping and provides some good background.

From McBSP Channel Swapping:  Section: Background "This problem only occurs when the McBSP is the transmit frame slave (external device generates FSX) ."

The McBSP is not configued as the transmit frame slave, but the channel swap is still occuring. Any recommendations preventing the channel swap for this configuration?

PCR (0x01d0_2024)  is configured as : 0x0000_0a0f and the SRGR (0x01d0_2014) is 0x103f_1f03.

 

 

 

  • 0
    TI__Expert 5955 points

    Hi,

    All the three causes documented in the mentioned wiki page could very well be applied to this case whereas the McBSP configured as the transmit frame master.

    Thanks,

    -Tai Nguyen

  • 0 in reply to Tai Nguyen
    Prodigy 90 points

    SPRUFI3A.pdf "TMS320DM36x Multichannel Buffered Serial Port (McBSP) Interface, March 2009 - Revised August 2009, Section 2.11.1 provides general initialization procedures. There are specifics for transmit and frame sync, sections 2.11.2, 2.11.2.1, 2.11.2.2, but nothing specific for receiving.

    The test case has the DM365  configured for receiving the video and audio which is encoded and written into a file. The transmit is not enabled. The file is copied to a PC and using VLC played. Rebooting the DM365 and repeat the encode. When playing back the file on the PC, the audio channels are swapped sometimes. 

    Are there specific initialization steps applicable for the receive path which is encoding?

    Code base is MVPRO 5.0, and I did implement modifications for the transmit case in sound/soc/davinci/davinci-i2s-mcbsp.c

     

     

  • 0 in reply to Curtis4590
    TI__Prodigy 635 points

     

    TI Team,

    Can you assist with above for my customer?

    They do not have a test case that always produces an audio channel swap. An example: 4 out of 5 times from a power-on they can record and when playing back the file on the PC the audio is heard on left speaker, and once on the right speaker. When recording this is the receive path to the DM365.  They have not found any comments in the McBSP User’s Guide or TI forum that discuss this path – only the transmit and corrections for XSYNCERR.