Media coding for loss recovery with remotely predicted data units

摘要

An improved loss recovery method for coding streaming media classifies each data unit in the media stream as an independent data unit (I unit), a remotely predicted unit (R unit) or a predicted data unit (P unit). Each of these units is organized into independent segments having an I unit, multiple P units and R units interspersed among the P units. The beginning of each segment is the start of a random access point, while each R unit provides a loss recovery point that can be placed independently of the I unit. This approach separates the random access point from the loss recovery points provided by the R units, and makes the stream more impervious to data losses without substantially impacting coding efficiency. The most important data units are transmitted with the most reliability to ensure that the majority of the data received by the client is usable. The I units are the least sensitive to transmission losses because they are coded using only their own data. While they provide the best coding efficiency, the P units are the most sensitive to data loss because the loss of one P unit renders useless all of the P units that depend on it. The remotely predicted units are dependent on the I unit, or in an alternative implementation, on another R unit.

主权项

1. A computer system comprising:
frame buffers; and a video encoder configured to:
classify plural frames of an input stream into plural layers of a hierarchy having dependency relationships, the plural layers including:
a layer of intra-coded frames in which each intra-coded frame includes only blocks encoded without using motion compensation;one or more successively higher layers of remotely predicted frames in which each remotely predicted frame in any given layer includes blocks that (a) can be encoded using motion compensation with remote prediction relative to a reference frame in the layer of intra-coded frames, the given layer or a lower layer of the one or more layers of remotely predicted frames, and (b) cannot be encoded with motion compensation relative to a reconstructed version of an adjacent frame that immediately preceded the remotely predicted frame in the input stream; anda layer of predicted frames in which each predicted frame includes blocks that can be encoded using motion compensation with non-remote prediction relative to a reference frame in the layer of intra-coded frames, the one or more layers of remotely predicted frames or the layer of predicted frames;encode the plural frames to produce encoded video, wherein the video encoder is configured to, for a current frame in the one or more layers of remotely predicted frames:
select, from among plural reference frames in the frame buffers, one or more reference frames to be used in motion compensation for the current frame;determine an identifier of the one or more reference frames to be used in motion compensation for the current frame; andupdate the plural reference frames in the frame buffers; andoutput the encoded video in a data stream, wherein the encoded video includes the identifier of the one or more reference frame to be used in motion compensation for the current frame.