Video frame alignment in adaptive bitrate streaming
Systems, apparatus and methods can operate to generate frame aligned digital video streams encoded at different bitrates from a common digital video stream. To provide uninterrupted playback of video content when a device switches from one stream encoded at one bit rate to the same digital video stream encoded at another bitrate, the video frames of the digital video streams can be aligned. To provide for proper frame alignment between fragments representing the same frame of a digital video stream encoded at different bitrates, video encoding device(s) can mark decoded digital pictures for subsequent encoding at different bit rates when the division of a program reference clock value by the fragment period approaches an integer value.
1. A system, comprising:
one or more video transcoding devices operable to receive a common digital input video stream wherein the video transcoding devices comprise:
a decoder operable to decode the common digital input video stream and generate a plurality of digital decoded pictures;
a frame marker operable to receive the digital decoded pictures and generate marked and non-marked digital pictures; and
an encoder operable to receive the marked and non-marked digital pictures and generate a plurality of frame aligned fragmented digital output video streams encoded at different bitrates comprising a plurality of encoded video frames;
wherein the encoder is further operable to begin each fragment with a marked digital picture encoded as an instantaneous decoding refresh reference (IDR)-frame,
wherein the frame marker marks the first digital picture received,
wherein the frame marker marks subsequent digital pictures, wherein the division of a program clock reference value associated with the digital decoded pictures by a fragment period is one of an integer value and approaching an integer value,
wherein the one of integer value and approaching an integer value is determined through a slope change in an analysis of program clock reference distribution values associated with the decoded digital pictures, and
wherein the program clock reference distribution is calculated as PCRdistribution=PCR/Int (PCR/Fragment Period).
2. The system of claim 1 , wherein the frame aligned fragmented digital output video streams is encoded in one of MPEG2, MPEG4, H.264, H.265 and open container format (Ogg).
3. The system of claim 1 , wherein a video server stores the frame aligned fragmented digital output video streams encoded at different bitrates.
4. The system of claim 3 , wherein the one or more video transcoders are integrated with the video server.
5. The system of claim 1 , wherein at least one of the video transcoder devices comprises one or more video decoders, frame markers and video encoders.