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Can TI816x support 8-ch video decoder ?

Wonhong Kwon
Intellectual 260 points
Other Parts Discussed in Thread: TVP5158

Hi,

Now, I'm using VS2 demo application (SDK 1.4) on our own custom board. The board has two 8-ch video decoders manufactured by Techwell (TW2868) instead of using four 4-ch TVP5158 decoders on EVM.

When I set the decoders as below, videos for all 16 channels are playing successfully.

[Settings]
VIP1_PORTA: BT656 Channel ID 1 ~ 4 from first 8-ch video decoder
VIP1_PORTB: BT656 Channel ID 1 ~ 4 from first 8-ch video decoder
VIP2_PORTA: BT656 Channel ID 1 ~ 4 from second 8-ch video decoder
VIP2_PORTB: BT656 Channel ID 1 ~ 4 from second 8-ch video decoder

However, when I set the decoders as below, only videos for the channels which have channel ID 1 ~ 4 are playing.

[Settings]
VIP1_PORTA: BT656 Channel ID 1 ~ 4 from first 8-ch video decoder
VIP1_PORTB: BT656 Channel ID 5 ~ 8 from first 8-ch video decoder
VIP2_PORTA: BT656 Channel ID 1 ~ 4 from second 8-ch video decoder
VIP2_PORTB: BT656 Channel ID 5 ~ 8 from second 8-ch video decoder

So, I'm gussing that demo application cannot interpret the input when the external video decoders send the data with channel ID 5 ~ 8. If not, how can I configure the demo application to enable channel ID 5 ~ 8 ?

Regards,
Wonhong

  • 0
    TI__Genius 9101 points

    I am assuming techwell device outputs in pixel mux mode.

    TI81xx supports upto 4CH D1 on each 8-bit port.

    In pixel mux mode the video decoder puts the chID either in the lower nibble of FVH codeword or in the lower nibble of Hblank region.

    TI81xx expects chID in pixel mux mode to be in the range of 0x0 to 0x3.

    Please check that the tech well device also uses these chID's in the BT656 data stream, else TI18x will not be able to decode it.

    In order to check further, if possible, pease send the techwell datasheet or atleast part of the datasheet which has this chID information.

    regards
    Kedar

  • 0 in reply to Kedar Chitnis
    Intellectual 260 points

    Hi Kedar,

    Yes, techwell device is using pixel mux mode. Also, TVP5158 and techwell device use the same way to handle channel ID information in the BT656 data stream.
    We've figured out that only channel ID 0x0 ~ 0x3 can be handled by TI816x and when we made some changes on HDVPSS driver we could see the video with channel ID 0x4 ~ 0x7.

    Regards,
    Wonhong

  • 0 in reply to Wonhong Kwon
    TI__Genius 9101 points

    Great ! Can you tell me what change you did in the drivers. We'll try to have this control at driver interface rather than modifing inside the driver.

    ~Kedar

  • 0 in reply to Kedar Chitnis
    Intellectual 260 points

    Hi Kedar,

    We've changed on hdvpss_01_00_01_25/packages/ti/psp/vps/drivers/capture/src/vpsdrv_captureApi.c and the changes are as below.

    Int32 Vps_captCreateChObj ( Vps_CaptObj * pObj )
    {
          ...
                /*
                 * make driver channel number from instance ID, stream ID,
                 * thus given driver channel number we can know which
                 * instance, stream, channel it belongs to
                 * chID
                 */
                pChObj->lChannelNum =
                    Vps_captMakeChannelNum ( pObj->instanceId, streamId, chId & 0x3);

          ...
    }

    Regards,
    Wonhong

  • 0 in reply to Wonhong Kwon
    Prodigy 160 points

    Dear Sir,

    I found the following description from HDVPSS document.

    When either Video Input Port is connected to an external device which is operating in
    “Pixel Mux Mode”, the lower 2 bits for the channel ID must be unique for each camera
    source. Pixel Mux Mode can operate in either 2x (2 camera) or 4x (4 camera) mode.
    VPDMA uses the 2 LSBs of the channel ID (camera ID) to determine which internal buffer
    to extract the video data into. The camera ID is a 5 bit field indicating which source the
    camera came from. Since the lower 2 bits are used for determining which internal buffer
    to send data to, this constraint must be maintained. For example, in this mode, you
    cannot have camera source IDs of 0, 4, 8 and 16.

    Is that means the channel number could not be 0, 4, 8 and 16?

    In the upper discussion the channel number start from 0 to 3.

    Best regards,

    Albert Ke