Changing the output to 720p/23.98 or 720p/24 fails

Hi,

Can you please try running at 720P60 and make sure that it works. 720P24 and 720P23.98 are not supported resolutions. Also try connecting it to monitor (DVI Sink) instead of TV for 720P24 and 720P23.98.

Regards,

Hardik Shah

Just to clarify the statement "720P24 and 720P23.98 are not supported resolutions"...

The 816x can happily output 720P24 or any other resolution desired, but there are a few things you need to consider.

First, very few monitors are able to display these resolutions so make sure that your monitor supports the resolution.

Second, the timing information you provided to the /timings entry is not the correct way to achieve 720p24. You are trying to decrease the frame rate by extending the blanking period. A better way is to reduce the pixel clock.

What display are you trying to connect to? 720p24/23.98 is neither a CEA nor VESA standard so virtually no consumer display will accept a signal of this resolution/frame rate.

What actually is your objective?

BR,

Steve

Hardik,

> Can you please try running at 720P60 and make sure that it works

Yes, the following all work:

• 720p60       ("74250,1280/110/220/40,720/5/20/5,1")
• 720p59.94 ("74176,1280/110/220/40,720/5/20/5,1")
• 720p50       ("74250,1280/440/220/40,720/5/20/5,1")
• 720p30       ("74250,1280/1760/220/40,720/5/20/5,1")
• 720p29.97 ("74176,1280/1760/220/40,720/5/20/5,1")

> Also try connecting it to monitor (DVI Sink) instead of TV for 720P24 and 720P23.98.

I have two devices that I'm plugging into that are known to support these rates - one made by our company and a Sony TV.  For example, they have no problem playing them from a QuauntumData QD780.

Dan -

Steve,

> The 816x can happily output 720P24 or any other resolution desired

Thanks for the clarification - will stand down from panic mode.

> First, very few monitors are able to display these resolutions so make
> sure that your monitor supports the resolution.

I have two devices that can display these resolutions.

> the /timings entry is not the correct way to achieve 720p24. You are trying
> to decrease the frame rate by extending the blanking period.

True. This is how we set up our previous products, based on the definition in
SMPTE 296M, where the luma sample periods per line is 4125, and the total lines
per frame is 750.

> 720p24/23.98 is neither a CEA nor VESA standard

Not true. They are originally defined in SMPTE 296M, but are also listed in
CEA-861E as VIC 60 (page 28 and 44). But, as it turns out, the entry on page 44
has a foot note where it says that CEA will use the 720p30 timing with reduced
pixel clock, as you suggest. Using the CEA timings appears to work:

• 720p/23.98:    59281,1280/1760/220/40,720/5/20/5,1
• 720p/24:          59400,1280/1760/220/40,720/5/20/5,1

The SMPTE timing is good for compatibility with the SDI outputs, which need the
74.25 ot 74.25*1000/1001 pixel clock. But this setup may be good enough for us.

> What actually is your objective?

Our product has to support a number of HDMI output resolutions, including these two.
My plan was to ignore the pre-built sysfs "/mode" controls, and stick exclusively to
defining the "/timings". So far, this has worked out without too much issue, except
for TI's bad VIC code lookup, and the HDMI audio support.  (Both reported separately.)

Anyway, thanks for the reply,

Dan -

Dan,

I have a feeling that the issue might be that the 720p24 specified front porch times greater than 2048 (2585). I would not initially expect this to be an issue since the registers are 12 bit, but given that the 60 & 30 fps modes work with extended blanking times it is a possibility.

I will check in to this to see if there is either a hardware or software limitation.

BR,

Steve