Portsdown software version 201803061 introduces proper support for some Logitech Webcams. The only versions tested so far are the Logitech C170 (a very old basic 640x480 device), the Logitech C310, the Logitech C525, the Logitech C910 and the Logitech C920 (full HD with internal H264 encoding).
In Portsdown Stretch (the current latest software), the use of a Webcam with the RPi Camera connected requires that the webcam is unplugged at boot, and only plugged in once the Portsdown has booted up. This is because of an incompatibility between the way that the RPi Camera drivers are loaded and the way that the Webcam drivers are loaded. This problem could be corrected if anyone is prepared to develop suitable udev rules to sort it out. It is beyond the capability of the current Portsdown team - any volunteers?
There is no issue if the RPi Camera is not connected.
Note that if you do boot-up with the Webcam and Pi Camera both connected, the Portsdown will not cleanly shutdown. It hangs half-way through shutdown, but may then be safely powered off.
Normal Webcam Modes
In the normal webcam modes, the webcam acts just the same as any video source and can be encoded in MPEG-2 (with audio) or H264 (without audio). Some Webcams will also work at 576p and 720p widescreen resolutions.
The normal Webcam modes have been tested with The Logitech C170, C525, C910 and C920. They should work with the Logitech C270. If you have another Logitech webcam that you would like included please report it on the BATC Forum and we will try to modify the software for compatibility.
Selecting Webcam as the source from the source menu will take the video input from the Webcam and output it at close to the selected resolution. Many Webcams are limited to set resolutions and you may find that the image size produced in 4:3 mode is 640x480 rather than 720x576. The mono audio from older webcams is reproduced as a single channel and the stereo audio from the C910 and C920 is reproduced as stereo (in MPEG-2 modes).
At the end of a transmission using the Logitech C270, C525 or C910 the camera driver needs time to be reset. During this 3 second reset process, the touchscreen does not respond to commands. After the reset, the touchscreen is re-enabled.
C920 H264 Webcam Mode
The Logitech C920 can output H264 encoded video with audio at a fixed bit rate. The Portsdown software has been modified to accept this stream and transmit it. Just select C920 as the video source, H264 encoding and then select the resolution that you want. As the stream is at a fixed bit rate of 3.4 MBit/s (for all resolutions), the Portsdown needs to be set up to transmit at 2MS or more, 7/8 FEC. TRANSMISSIONS AT LOWER SRs and FECs ARE UNLIKELY TO WORK.