Adaptive streaming transcoder synchronization

摘要

Techniques for synchronizing streams in an adaptive streaming environment include cross-chassis and intra-chassis synchronization of video and/or audio. In an adaptive streaming system that streams content in segments or chunks at varying levels of quality corresponding to different coding rates, implementations enable seamless switching between transcoded audio output streams. The streams synchronized may be those that have been ingested by the transcoder in a compressed format and transcoded into a different compressed format, as part of the transcoding process. The transcoded audio output streams may be synchronized such that audio frame boundaries contain identical pulse-code modulation (PCM) samples, packetized elementary stream (PES) location, and presentation time stamp (PTS) value.

主权项

1. A system for inter-chassis synchronization between audio output streams, the system comprising:
a first adaptive transcoder in a first chassis for generating multiple transcoded audio output streams from an input to the first adaptive transcoder, and synchronizing the multiple transcoded audio output streams based on corresponding segments; a second adaptive transcoder in a second chassis, the second adaptive transcoder including:
at least one input for receiving an input having audio content matching audio content in the input to the first adaptive transcoder;one or more transcoding processors generating multiple transcoded audio output streams from the input stream and synchronizing the multiple transcoded audio output streams representations based on corresponding segments, wherein each transcoding processor has an audio encoder for inserting presentation time stamps in the segments of the transcoded audio output streams; the second chassis synchronizing a second group of transcoded audio output streams output from the second transcoder with a first group of transcoded audio output streams output from the first transcoder by: receiving, from the first chassis, video segment presentation time stamp and corresponding audio aligned presentation time stamp pairs for the input to the first adaptive transcoder; storing the pairs of video segment presentation time stamp and audio aligned presentation time stamp data from the first chassis to a memory location in the second chassis designated for first transcoder sync information; identifying and storing video segment presentation time stamp and corresponding audio aligned presentation time stamp pairs for the input to the second adaptive transcoder to a memory location in the second chassis designated for second transcoder sync information; for a video segment presentation time stamp received at the input to the second transcoder, searching for a first transcoder video segment presentation time stamp in the memory location designated for first transcoder sync information that matches the video segment presentation time stamp received at the input at the second transcoder compare an audio aligned presentation time stamp paired to a matching first transcoder video segment presentation time stamp to a second transcoder audio aligned presentation time stamp paired with the received video segment presentation time stamp; determine an audio sync presentation time stamp offset based on the difference between the first transcoder's audio aligned presentation time stamp to the second transcoder's audio aligned presentation time stamp; and based on the audio sync presentation time stamp offset, adjusting the presentation time stamp inserted by the audio encoder in segments of the transcoded audio output streams to synchronize the transcoded audio output streams output from the second transcoder with the transcoded audio output streams output from the first transcoder.