Difference between revisions of "C920 Webcam"

From BATC Wiki
Jump to navigation Jump to search
 
(5 intermediate revisions by 2 users not shown)
Line 3: Line 3:
 
[[File:Logitech C920.jpg|400px]]
 
[[File:Logitech C920.jpg|400px]]
  
The Logitech C920 Webcam can be used with the Portsdown transmitter for both video and sound.  Note that the Webcam is used in native "uvcvideo" mode, and its on-board H264 encoder is not used; this is because the output bitrate of the H264 encoder cannot be directly controlled to match DATV symbol rates and FECs.
+
The Logitech C920 Webcam can be used with the Portsdown transmitter for both video and sound.  It can be used in 3 modes: as a normal webcam providing images for MPEG-2 transmission with sound (either SD or 720p), as a normal webcam with H264 SD pictures and sound being encoded by the Raspberry Pi, or using its internal H264 encoder to transmit pictures at SD, 720p or 1080p with sound.  For internal H264 encoding modes, the bitrate is fixed and the Portsdown MUST be selected to DVB-S, 2 MS or more, 7/8 FEC and be using a Filter-modulator board for this to work.
  
===Constraints===
+
===Compatibility===
  
The C920 Webcam is used in place of the analog video capture dongle, which '''MUST''' be disconnected prior to booting up with the C920 connected.
+
In Portsdown Stretch (pre 201902072), 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. There is no issue if the RPi Camera is not connected.
  
The correct source to select is "Comp Vid"
+
The incompatibility issue has been resolved since Portsdown Stretch update 201902072 and the two cameras should now co-exist.
  
The image size transmitted in MPEG2 mode is 800x600 pixels; in H264 mode it is the standard 704x576 pixels.
+
===Power Requirements===
  
The audio source must be selected to "EasyCap"Auto does not always work.
+
The C920 is quite power-hungry and can be the straw that breaks the Camel's back in the RPi power budget, leading to under-voltage events with unpredictable consequencesFor best results, use a powered USB Hub, or at least make sure that your RPi PSU is up to the job.  Remember that you can check if there have been any power events from the Info screen on Menu 2.

Latest revision as of 20:51, 30 March 2020

Using the C920 Webcam With the Portsdown

Logitech C920.jpg

The Logitech C920 Webcam can be used with the Portsdown transmitter for both video and sound. It can be used in 3 modes: as a normal webcam providing images for MPEG-2 transmission with sound (either SD or 720p), as a normal webcam with H264 SD pictures and sound being encoded by the Raspberry Pi, or using its internal H264 encoder to transmit pictures at SD, 720p or 1080p with sound. For internal H264 encoding modes, the bitrate is fixed and the Portsdown MUST be selected to DVB-S, 2 MS or more, 7/8 FEC and be using a Filter-modulator board for this to work.

Compatibility

In Portsdown Stretch (pre 201902072), 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. There is no issue if the RPi Camera is not connected.

The incompatibility issue has been resolved since Portsdown Stretch update 201902072 and the two cameras should now co-exist.

Power Requirements

The C920 is quite power-hungry and can be the straw that breaks the Camel's back in the RPi power budget, leading to under-voltage events with unpredictable consequences. For best results, use a powered USB Hub, or at least make sure that your RPi PSU is up to the job. Remember that you can check if there have been any power events from the Info screen on Menu 2.