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 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
