Hello, I am working on the linux driver for our new video capture board and facing some compatibility problem which seems to be related to unclear language in the V4L specification. The device supports a larger number of inputs, but with a different set of standards on each of them. Now, the problem is that ffmpeg is using VIDIOC_ENUMSTD/VIDIOC_S_STD before VIDIOC_S_INPUT. So the driver has to give a list of supported standards before knowing which input the device will be taking. Currently I am experimenting with a workaround to remember the set standard and then failing on VIDIOC_S_INPUT when not compatible, but this seems to create more problems than it solves. I have the feeling that this behaviour is not covered by the specification, and it makes the driver unnecesarily complex. In my opinion, the standard is broken: on page http://v4l2spec.bytesex.org/spec/r11217.htm, it says: "It is good practice to select an input before querying or negotiating any other parameters." It should be changed to "Aplications must...", and ffmpeg needs fixing to call VIDIOC_S_INPUT before VIDIOC_ENUMSTD. I hope to get some opinion from you, if this is the right approach or not. Best regards, Rupert Eibauer -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
