Simultaneous Digital Video Output in DM8148

Hi Ravindra,

We could have BT1120 output from DVO1/2 but we cannot have two BT656 outputs from DVO1/2, also the input to the DVO1/2 is single, so even if you output two BT656, the input same..

Regards,

Brijesh Jadav

Hello Brijesh,

I replied back on the use-case that we are currently developing and wanted to konw the feasibility of the same with Dm8148.

We need to enable both DVO1 and DVO2 simultaneously each operating in dual-frame BT656 Format. I wanted to know if this is possible with DM8148 or is there a roadmap for implementing the same in a future version of DM series.

If this is not possible, can we enable only one i.e., DVO1 in single frame BT656 form and keep alternatively switching between four different video buffers/frames.

Thanks,
Ravindra

Hello Ravindra,

As i said, we cannot have dual BT656 output from DVO1/2, it supports BT1120 output, you could treat each of the input stream as either luma and chroma and then send it out, but my worry is input to VENC is RGB and YUV422 is first converted into YUV444 and then converted to RGB, you may loose your actual data, so i would not suggest doing this.

Regards,

Brijesh Jadav

Brijesh,

Thanks. So you are suggesting that we cannot have both DVO1 and DVO2 working at the same time in 656 format. I was going through the VPSS Guide below:

http://processors.wiki.ti.com/index.php/DM814X_AM387X_VPSS_Video_Driver_User_Guide_PSP_04.01.00.05

The section on VPSS Display :Display output shows a table which reads as:

Arguments                Definition
single                        An 10-bit wide, single channel CCIR656 video stream
double                      Two 10-bit wide video streams in CCIR656 format. The video data is YUV422 format
triple                         Three channel 10-bit video streams with embedded sync SAV/EAV. The video format can be YCbCr 444 or RGB

From the above table, I was assuming that we can configure DVO1 in 2 video stream CCIR656 Format. Extending the above, I want to use both DVO1 and DVO2 at the same time and both operating in 2 Video Stream CCIR656 format. Is this possible??

From the above Wiki link, I infer that both DVO1 and DVO2 can be enabled/powered on at the same time. This has been explained under

Cloning /dev/video1(video0) output to both vcompmux-HDMI VENC(display0) and vcompmux-DVO2 VENC(display1)

Regards,
Ravindra

hi Ravindra,

the only difference between BT565 and BT1120 is bt565 is 8 bit embedded sync format with Luma and chroma are interleaved. whereas BT1120 is 16 bit embedded sync format in which luma and chroma comes on separate lines. So here double channel bt656 means bt1120, in this case, we cannot have independent 2 bt656 streams from DVO1/2.

You could definately tie DVO1 and DVO2 to get synchronous output from both.

Regards,

Brijesh

Brijesh,

Thanks for the clarifications on BT1120 and BT656 format.

Since our Application accepts 4 different compressed video streams from Network, we wanted to decode them on the Cortex-M3 and then output them using the DVO1 and DVO2. Can the Tiler be used for this operation to send out 4 different streams using just the DVO1 itself.

The objective is to have both DVO1 and DVO2 operate together [which we know is possible] and they sending different data out [which you said is not possible since the inputs to both DVO1 and DVO2 is same].

Regadrs,
Ravindra

Hi Ravindra,

As i said, DVO supports only single BT1120 or single BT656, it does not support dual bt656. this has nothing to do with tiler..

Regards,

Brijesh Jadav

Brijesh,

Thanks for the immediate response. I believe my understanding on the Tiler is wrong. I will study the Tiler chapter once again to understand its usage better.

So the summary is that we can enable both DVO1 and DVO2 to operate simultaneously, but both can send out only a common video frame in 656 format, it is not possible for them to send out different video streams at the same time.

Regards,
Ravindra

Hi Ravindra,

Ok, both DVO1 and DVO2 can send the output simulteneously. There is not change required in this case, you just need to connect your input paths to the correct VENC.

Change is required when you want both the VENCs to be in sync. this is right now supported..

Regards,

Brijesh