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   hiroh: I would like to clarify the meaning of V4L2_CID_MPEG_VIDEO_BITRATE and V4L2_CID_MPEG_VIDEO_BITRATE_PEAK when a bitrate mode is VBR.
   <br> In CBR encoding, V4L2_CID_MPEG_VIDEO_BITRATE_PEAK is just ignored and a driver does their best to produce a bitstream whose bitrate is specified with V4L2_CID_MPEG_VIDEO_BITRATE.
   <br> In general of VBR encoding, a range of bitrates is configured. I think we should set V4L2_CID_MPEG_VIDEO_BITRATE_PEAK to the max bitrate.
   <br> But I wonder what we should set V4L2_CID_MPEG_VIDEO_BITRATE. Is it the average of the bitrate, or the min? If it is the average, how the minimum bitrate is computed in a driver?
   hverkuil: <u>hiroh</u>: it's the average bitrate. That could be clearer in the documentation, I'll make a quick patch for that.
   <br> The documentation for V4L2_CID_MPEG_VIDEO_BITRATE_PEAK actually refers to V4L2_CID_MPEG_VIDEO_BITRATE as the average video bitrate, but 'average' is missing in the V4L2_MPEG_VIDEO_BITRATE doc itself.
   hiroh: Thanks. How does a driver decide a minimum bitrate from the average and max in VBR encoding?
   hverkuil: <u>hiroh</u>: That's driver/firmware/hardware specific.
   hiroh: I see. Is there any recommended way of computing the average value from min and max?
   hverkuil: If there is hardware that supports a minimum video bitrate, then there would be a good case for adding a new control for that. Haven't heard about anything like that, though.
   <br> Not a clue :-)
   hiroh: Hmm, it is something like ABR actually.
   <br> https://en.wikipedia.org/wiki/Average_bitrate
   <br> IMO, ABR is good if multi-pass encoding is allowed. But I think v4l2 encoder can do single-pass encoding.
   <br> Anyway, thanks for clarifying.
   tomba: I want to split a sensor subdev into two subdevs, but I'm a bit confused... Do I need to linux devices to represent those subdevs? I can't just create "virtual" subdevs?
   hverkuil: <u>ezequielg</u>: I discovered why my test build didn't catch the kerneldoc issues in the vp8 series: it will find kerneldoc issues in sources (happens automatically when you add W=1 to make), but the headers are not checked. As far as I can tell you need to do that manually.
   <br> I added code to my build script to do that for all media headers, and got about 1000 warnings and errors :-)
   <br> 1158 to be precise
   ezequielg: <u>hverkuil</u>: ouch ^_^
   v4lusr: anybody here know abotu rate control ?
   ***: koike1 has left