Hi Hiro, On Fri, Nov 13, 2020 at 6:04 PM Hirokazu Honda <hiroh@xxxxxxxxxxxx> wrote: > > Hi, > > According to the official v4l2 encoder driver usage description [1], > v4l2 steatful encoder driver doesn't have a guarantee when frames fed > to a driver will be returned. > To make sure all pending frames are output by the driver, an app must > call VIDIOC_ENCODER_CMD with cmd=V4L2_ENC_CMD_STOP. > However, it is not mandatory to support the command in the current > v4l2 stateful encoder API specification. > An app can check it by VIDIOC_TRY_ENCODER_CMD beforehand. > My question is when an app has to get all the frames of an encoder > sequence, how we can achieve this without V4L2_ENC_CMD_STOP support. > This demand is natural and in fact WebCodecs [2] requires this. > > I think there are two options, > 1.) Ensure that a driver will eventually output frames if it doesn't > support V4L2_ENC_CMD_STOP. > 2.) Change V4L2_ENC_CMD_STOP support to be mandatory Unless I am missing the part of the spec that says the contrary, V4L2_ENC_CMD_STOP is part of the encoder specification, and thus is mandatory. Some older drivers might not have support for it, in such cases the correct course of action would be to fix them. > > Any comments are appreciated. > Thanks so much in advance. > > [1] https://www.kernel.org/doc/html/latest/userspace-api/media/v4l/dev-encoder.html#drain > [2] https://web.dev/webcodecs/ > > Sincerely, > -Hiro
