Method and an apparatus for mixing compressed video
View Patent ↗A system for controlling a conference that takes input streams from a variety of sources, at least some of the streams having a relatively low-resolution, and composes the input streams into a single output stream of a relatively high-resolution. In doing the conversion the system takes intra Macro Blocks (MBs) of the input stream and produces inter output frames. As part of the conversion process, the system converts the Groups Of Blocks (GOBs) that have GOB headers into slices.
1. A method for use in composing a plurality of compressed video input streams, at least one input stream having a first resolution, into a single output stream in another resolution that is higher than the first resolution, the method comprising:
receiving a request to transmit a high resolution intra frame to a requesting endpoint;
in response, requesting a low resolution intra frame from a transmitting endpoint;
converting the low resolution intra frame into intra macro blocks of an inter frame;
transmitting a high resolution intra background frame to the requesting endpoint; and
transmitting the macro blocks to the requesting endpoint as a set of consecutive high resolution inter frames.
2. The method of claim 1 , wherein at least one of the plurality of compressed video input streams has been compressed according to a compression standard selected from a group consisting of H.263 and MPEG 4.
3. The method of claim 1 , wherein the first resolution includes at least one type of resolution selected from a group consisting of QCIF, CIF and 4CIF.
4. The method of claim 1 , wherein the other resolution includes at least one type of resolution selected from a group consisting of CIF, 4CIF and 16CIF.
5. The method of claim 1 further comprising: converting at least one of the plurality of compressed video input streams into H.263 Annex K compression standard.
6. The method of claim 1 wherein the composing further comprises converting Groups Of Block (GOB) headers in the compressed video input streams into slice headers in the single output stream.
7. A method comprising: composing a plurality of compressed video input streams, each stream having an input resolution, into a single output stream of an output resolution that is higher than the input resolution of the compressed video input streams, by at least
converting the plurality of compressed video input streams into high-resolution H.263 with Annex K compression standard, if the compressed video input stream is not already in a format based on the H.263 with Annex K standard;
converting Groups Of Blocks (GOBs) headers in the compressed video input streams into slice headers, if the compressed video input stream is not already in a format based on the H.263 with Annex K standard; and
responding to a video update request from a receiver by transmitting an intra background frame; requesting a low resolution intra frame from a transmitting endpoint; sending a high resolution intra background frame to the receiver; converting the low resolution intra frame into intra macro blocks of an inter frame; and transmitting the macro blocks to the requesting endpoint as a set of consecutive high-resolution inter frames.
8. A system comprising:
a plurality of conference modules, each conference module including
(I) a shared memory having buffers;
(II) a plurality of input modules associated with a plurality of input streams, a plurality of parsers, a plurality of depacketizers, and a plurality of linked lists, each of the input modules having at least
(A) one of the plurality of depacketizers that depacketizes one of the plurality of input streams of a first resolution, which is divided into Groups Of Blocks (GOBs) or slices from a network,
(B) one of the plurality of parser that
(1) converts the GOBs' headers into slice headers,
(2) converts intra frames of the first resolution into inter frames of a second resolution that is higher than the first resolution,
(3) generates recommended division points,
(4) delivers a converted stream in portions to the buffers, where the converted stream is a compressed video stream of the second resolution having the inter frames of the second resolution and the slice headers, and
(5) generates at least one of the plurality of linked lists, each linked list being a list of pointers pointing to where corresponding ones of the portions are stored in the buffers;
(III) a plurality of output modules for processing the buffers designated in the plurality of linked lists, the plurality of input streams being associated with the buffers and each of a group of the plurality of output modules composing at least part of the plurality of input streams into one output stream of the second resolution, each output module having at least
(A) a background buffer for storing information associated with empty screen parts of the output stream, and
(B) a packetizer for dividing the output stream into packets and sending the packets via the network to endpoints; and
(IV) a conference manager that
(A) communicates with a host regarding how to layout a conference, and
(B) assigns the group of input modules to the output module.