Method and apparatus for decoding a data stream in audio video streaming systems
View Patent ↗A method for decoding a data stream containing audio/video substreams and control substreams comprises buffering nodes having the possibility to buffer multiple data packets in the same buffer. This may be achieved by having separate parameters for the allocated buffer size and any stored packet. Thus, not only multiple packets may be stored in the buffering node, but also such node may exist while its buffer is empty, so that the node may be reused later. This is particularly useful for buffering and selectively accessing multiple audio packets in MPEG-4 audio nodes or sound nodes.
1. Method for decoding a data stream containing a first and a second substream, the first substream containing first and second multimedia data packets and the second substream containing control information, wherein the multimedia data packets contain an indication of the time when to be presented and are decoded prior to their indicated presentation time, the method comprising the steps of:
extracting from
said control information of the second substream first, second and third control data wherein
the first control data are suitable for defining buffer size to be allocated
the second control data are suitable for defining one or more second multimedia data packets to be buffered, and
the third control data are suitable for defining a mode for buffering the second multimedia data packets;
allocating, in a buffer, buffer size according to the first control data (Length);
storing the first decoded multimedia data packets in the buffer; and
storing one or more multimedia data packets according to the second control data in the buffer, wherein depending on the third control data either the second multimedia data packets are appended to the first decoded multimedia data packets in the buffer, or replace some or all of the first decoded multimedia data packets in the buffer.
2. Method according to claim 1 , wherein the third control data defines one of a plurality of operation modes, wherein in a first mode buffering of multimedia data packets is performed when the value of the first control data changes, and in a second and third mode the second control data are valid for specifying the multimedia data packets to be buffered, wherein in the second mode the multimedia data packets replace the buffer contents and in the third mode the multimedia data packets are appended to the buffer contents.
3. Method according to claim 2 , wherein the third mode has two variations, wherein in the first variation the buffering of multimedia data packets stops when the buffer is full, and in the second variation previously buffered data may be overwritten when the buffer is full.
4. Method according to claim 1 , wherein the method is utilized in an instance of a processing node and wherein the first control data defines the allocated buffer size at node creation time.
5. Method according to claim 1 , wherein labels are attached to the buffered first and other multimedia data packets, and the packets may be accessed through their respective label.
6. Method according to the claim 5 , wherein a label attached to the buffered data packets contains an index relative to the latest received data packet.
7. Method according to claim 1 , wherein the first substream contains audio data and the second substream contains a description of the presentation.
8. Apparatus for decoding a data stream, the data stream containing a first and a second substream, the first substream containing first and second multimedia data packets and the second substream containing control information, wherein the multimedia data packets contain an indication of the time when to be presented and are decoded prior to their indicated presentation time, and wherein the first and second multimedia data packets are buffered, comprising
buffering means for said buffering of the first and the second multimedia data packets;
means for extracting from said control information of the second substream first, second and third control data,
wherein the first control data are suitable for defining buffer size to be allocated,
the second control data are suitable for defining one or more second multimedia data packets to be buffered, and
the third control data are suitable for defining a mode for buffering the second a multimedia data packets;
means for allocating, in the buffer, buffer size according to the first control data;
means for storing the first decoded multimedia data packets in the buffer; and
means for storing one or more multimedia data packets according to the second control data in the buffer, wherein depending on the third control data either the second multimedia data packets are appended to the first decoded multimedia data packets in the buffer, or replace some or all of the first decoded multimedia data packets in the buffer.
9. Apparatus according to claim 8 , further comprising means for attaching labels to the buffered multimedia data packets, and means for accessing, retrieving or deleting the packets through their respective label.
10. Apparatus according to claim 8 , wherein the data stream is an MPEG-4 compliant data stream.
11. Method according to claim 1 , wherein replacing the stored first decoded multimedia packets with the second multimedia data packets further comprises the step of clearing the buffer before storing the second multimedia data packets.
12. Apparatus according to claim 8 , wherein the third control data defines one of a plurality of operation modes, wherein in a first mode buffering of multimedia data packets is performed when the value of the first control data changes, and in a second and third mode the second control data are valid for specifying the multimedia data packets to be buffered, wherein in the second mode the multimedia data packets replace the buffer contents and in the third mode the multimedia data packets are appended to the buffer contents.