Hi
The Raspberry PI TM image does not work on Blackmagic vision mixers when the cameras being used on the mixer are unable to be adjusted to 1080 60i. Vision mixers use one standard for all vision inputs. This is because the Pi TM assumes that the only standard is 60i. In countries that run on 50Hz we use 50i and is is common to come across cameras that cannot do 60i. Please could you add a very simple function to the RPi that would allow us to choose between 60i and 50i. The best way to do this would be to us the Digital IO pins on the RPi and use a jumper to set the standard. This would eliminate any need for complex user interface software changes and testing. An if/else statement in the boot function would do it and it would be a set and forget solution with default to 'no jumper then 60i for the USA.
Until this is done NZ and Australia are dead in the water as far as using RPi units on our AV systems.
I think the use case of the rPi was to drive displays on fields or video projectors. Also, I thought the rPi was configured 1080p output. I maybe mistaken.
Chris,
TM does not make that assumption, and yes weâre aware that other parts of the world use a 50Hz standard instead of 60. First, the TM-specific code on the Pi does absolutely nothing with the output resolution at all. Output resolution selection is done entirely by the VideoCore GPU on the Raspberry Pi and this happens before the ARM CPU is even started (i.e. before any of the operating system or TM code even has a chance to run).
Second, the configuration used by the TM Pi image for the VideoCore HDMI output is for the Pi to select an appropriate output resolution based on the capabilities reported by the receiving device (TV or monitor, or in your case your vision mixer). This is done using EDID data exchange - the receiver (mixer or TV) reports a list of video modes it supports, and the source (Pi GPU) picks the best one they both agree on and uses it. Defaulting the TM Pi image to auto-negotiate using EDID is the best choice we have to enable it to work out of the box with the widest array of display devices.
If the Pi is coming up in an inappropriate resolution when connected to your vision mixer, then the fault most likely lies with the mixer as it must not be reporting the resolution to the Pi that it apparently needs. Unfortunately this seems to be common with âproâ equipment. Some quick searching shows lots of threads of people struggling with Blackmagic Designâs switchers - they either provide incorrect EDID information or none at all depending on which site you read.
My recommendation would be to contact Blackmagic Design support to see if itâs possible to configure your mixer to report the proper formats that it needs.
If that doesnât work, you can change the configuration of the VideoCore GPU to cause it to force a specific output resolution. To do this youâll have to edit the config.txt file that lives on the Piâs SD card. By default in the TM Pi image, the output resolution is not set in order to enable the automatic negotiation. You can reference the Raspberry Pi documentation regarding video output options here . Going this route is obviously much less ideal than getting your video mixer to report the correct resolution over EDID, but maybe it can get you going for now. Unfortunately I canât make any guarantees about preserving those settings when new Pi TM updates become available, so if you do make those changes you might have to re-apply them after any updates.
Thanks you for such a detailed response and so fast! I really appreciate it. I will dig deeper now I understand more about the âengine of the PI TMâ I am sure I will find a resolution.
Very helpful response Dave! I thought we were locked in with regards to output options, but this definitely allows us to debug different video options without interfering with TM functions. Many thanks!