Hi Robert, thank you for your response, even if it sound a bit like zombie commercial :)
I took a look on the specification and feel like i need to put two bits of doubt concerning this webcam, just in case some one wont to by it. reference to: http://www.logitech.com/en-us/for-business/products/webcams-headsets/devices/b990-hd-webcam - Native 5MP HD sensor - High-definition video in 720p widescreen mode with recommended system - Color depth: 24-bit true color - Frame rate: Up to 30 frames per second streaming video in 720p and VGA mode Doubts: - 24-bit true color - i'm confused here, seems like we can access only 16-bit color over yuv. will it really do 24bit with h264? Even if it will cost more power?... i think it is not true - Even if it has 5MPixel sensor, seems like we have access only to 1MP. According to this http://pastebin.com/9WFgytwY the biggest resolution what it provide is 1280x720, in other words "High-definition video in 720p". This is also maximal resolution what can be uncompressed provided with ~15fps over USB2.0 . But it give us actually only 10 fps. JPEG compressed stream seems to be more realistic, it can indeed do 30 fps at HD720p. I guess it will take about 30Mbit/S bandwidth. Now after it sounds more realistic... H264 can reduce it even more (no doubt). In case of hardware encoder, we should be able to dynamically control encoding process, reduce keyframe frequency and be able to force KF if needed to recover the stream, (i guess you currently trying to find it out). And if you use gstreamer then, thelepythy+gstreamer should be able to control it as well. It looks like lots of work and fun. Suddenly i do not have this toy to play with it. I hope it is really worth it. Regards, Alexey. On 27.08.2011 19:47, Robert Krakora wrote: > Hi Alexey, > > As webcam sampling size increases (5MP in the case of the Logitech B990), > encoding in the camera becomes important to conserve USB bandwidth, and if > you want to transmit content over an Ethernet connection it is even more > important. Also, software encoding eats up host processor CPU. We have > Intel Atom based mediaports that employ NVidia hardware assisted decoding. > The are all equipped with cameras and software encoding would consume a fair > amount of the CPU. We push the encoded data around the network. > > If you have a mid->high end CPU, no problem, use a software encoder if you > wish. Just remember though, that your USB host controller + hub aggregate > bandwidth will be mostly consumed by the raw data of the camera. At some > point we will probably see USB 3.0 webcams to handle raw data from cameras > as sampling size increases. > > I can send you some samples, but as of today I cannot control the encoders > parameters, so it is not the highest quality, but still looks really good. > > Best Regards, > > Rob Krakora > > > On Sat, Aug 27, 2011 at 2:09 AM, Alexey Fisher > <[email protected]>wrote: > >> Am 26.08.2011 20:36, schrieb Robert Krakora: >> >>> Hello, >>> >>> Were you ever able to get H.264 content from the Logitech B990? I was >>> able to >>> using Stephan's patches and a patch to the v4l2src GStreamer element. I >>> have >>> both audio and video. However, I have not figured out how to affect the >>> encoding parameters that I believe are exposed by the XUs. If you are >>> interested, I can make what I have available for you. >>> >>> Best Regards, >>> >>> Rob Krakora >>> >> >> I'd really like to know, is it worth to do it. I mean what is the image >> quality? What kind of H.264 bitstream is created? What is the key frame >> frequency? Can you grub and send me some sample file? >> >> What actual use cases? If i understand correctly, it will be transcoded any >> way in case of videochat. To record myself i'd prefer software encoder, for >> better quality. >> > > > _______________________________________________ Linux-uvc-devel mailing list [email protected] https://lists.berlios.de/mailman/listinfo/linux-uvc-devel
