Patent ID: 8655143
Filing Date: 2014-02-18
Classification: H04N

Abstract:
1. A method of processing a program stream, the program stream comprising a video and an audio stream, the method comprising: initializing an audio reference clock to a value associated with a presentation timestamp for a decodable audio frame which is the first audio frame capable of being decoded in the audio stream; initializing a video reference clock to a value associated with a presentation timestamp for a decodable video frame which is the first video frame capable of being decoded in the video stream; storing audio frames received prior to receipt of the decodable video frame which is the first video frame capable of being decoded in the video stream in an audio frame buffer; starting the audio reference clock and the video reference clock after a video preroll delay elapses, wherein the video preroll delay is the difference between the first decodable video frame presentation timestamp and the value of a program clock reference at the time that the first decodable video frame presentation timestamp is received, wherein the presentation timestamp of the first audio frame is earlier than the presentation timestamp of the first video frame, wherein the video reference clock is configured to run at a slower rate than the audio reference clock, and wherein the video reference clock is normalized when the audio reference clock catches up with the video reference clock; decoding the audio stream in accordance with the audio reference clock; and decoding the video stream in accordance with the video reference clock.