Method and apparatus for transmitting a coded video signal

• US 20060050970A1
• Filed: 09/08/2004
• Published: 03/09/2006
• Est. Priority Date: 09/08/2004
• Status: Active Grant

• Current Assignee: Sony Corporation (Sony Group Corp.)
• Original Assignee: Sony Corporation (Sony Group Corp.), Sony Electronics Inc. (Sony Group Corp.)
• Inventors: Gunatilake, Priyan
• Granted Patent: US 7,983,160 B2
• Time in Patent Office: Days
• US Class Current: 382/232
• CPC Class Codes: H04N 19/149 by estimating the code amount by means of a model, e.g. mathematical model or statistical model
• CPC Class Codes: H04N 19/503 involving temporal prediction adaptive coding with adaptive selection between spatial and temporal predictive coding H04N19/107; adaptive coding with adaptive selection among a plurality of temporal predictive coding modes H04N19/109
• CPC Class Codes: H04N 21/23406 involving management of server-side video buffer
• CPC Class Codes: H04N 21/44004 involving video buffer management, e.g. video decoder buffer or video display buffer
• CPC Class Codes: H04N 21/6377 directed to server one-way streaming services wherein the source is controlled by the destination H04L65/613
• CPC Class Codes: H04N 21/658 Transmission by the client directed to the server

Abstract

A method and apparatus for transmitting a digitally encoded video image in real time via a data network wherein the video image is digitally encoded using a compression algorithm having a variable bit rate, e.g., JPEG2K, to provide an encoded data stream, the encoded data stream is fed into a buffer of known size, and the data is read from the buffer via a streamer with a controllable bit rate to provide a bit stream at a desired stream bit rate for transmission via the network. The bit rate of the encoded data stream from the encoder is monitored by a predictor and predicts a future bit rate of the encoded data stream; and, the bit rate of at least one of the encoder and the streamer is adjusted to provide the desired streaming bit rate.

Claims

1. A method of transmitting a coded video image in real time via a data network comprising:

encoding a video image using a compression algorithm having a variable bit rate to provide an encoded data stream;

feeding the encoded data stream into a buffer of known size;

reading data from the buffer via a streamer with a controllable bit rate to provide a bit stream at a desired stream bit rate for transmission via the network;

monitoring the bit rate of the encoded data stream from the encoder and predicting a future bit rate of the encoded data stream; and

,

adjusting the bit rate of at least one of the encoder and the streamer to provide the desired streaming bit rate.

2. The method according to claim 1, wherein the prediction is carried out using a prediction model that maps bit rate vs. time based on a second or higher order polynomial to ensure smoothness of the bit rate vs. time curve.

3. The method according to claim 1, wherein the encoding algorithm is a JPEG2k algorithm.

4. The method according to claim 1, further including defining a set of strip-wise constant bit rate streaming levels;

and wherein the adjusting includes raising and lowering the streaming bit rate proportionately to an increase or decrease of the predicted encoded bit rate level, using the set of step-wise streaming levels.

5. The method according to claim 4 further comprising enlarging the buffer size by a amount equal to the momentary encoded bit rate minus the momentary streaming bit rate when the streaming bit rate is set to a maximum value such that further increase would result in a buffer overflow condition.

6. The method according to claim 4 further including defining a relationship between the encoding and streaming bit rate as follows:

Encoding bit rate (n)=data input to buffer (n);

Data in buffer (n)=data in buffer (n−

1)+encoding bit rate (n)−

streaming bit rate (n);

Encoding bit rate (n)=delta (n)+streaming bit rate (n); and

delta (n)=data in buffer (n)−

data in buffer (n−

1)

7. The method according to claim 1, further including providing the encoding algorithm with a defined set of quality levels proportional to the encoding bit rate;

and wherein the adjusting includes decreasing the encoding quality level, and thus the encoding bit rate, if the predicted encoding bit rate is greater than a maximum streaming bit rate level.

8. The method according to claim 7, wherein the adjusting further includes increasing the encoding quality level, and thus the encoding bit rate, if the predicted encoding bit rate plus a given threshold value is less than the maximum streaming bit rate level, where the threshold value is an empirical number based on an analysis of representative video streams.

9. The method according to claim 1, further including providing the encoding algorithm with a defined set of quality levels proportional to the encoding bit rate;

and wherein the adjusting includes increasing the encoding quality level, and thus the encoding bit rate, if the predicted encoding bit rate plus a given threshold value is less than the maximum streaming bit rate level, where the threshold value is an empirical number based on an analysis of representational video streams.

10. A method of transmitting a coded video signal in real time via a data network comprising:

encoding a video signal using a compression algorithm, having a variable bit rate and a defined plurality of quality levels with corresponding differing bit rates, to provide an encoded data stream;

feeding the encoded data stream to a buffer of known size;

reading data from the buffer via a streamer with a controllable bit rate to provide a bit stream at a desired streaming bit rate for transmission via the network.

monitoring the bit rate (n) of the encoded data signal and predicting a future bit rate (n+1) of the encoded data stream based on the bit rate (n); and

,

decreasing the encoding quality level, and thus the encoding bit rate, if the predicted encoding bit rate (n+1) is greater than a maximum permitted streaming bit rate.

11. The method according to claim 10, further including increasing the encoding quality level, and thus the encoding bit rate, if the predicted encoding bit rate (n+1) plus a threshold value is greater than a maximum permitted streaming bit rate, where the threshold value is an empirically derived number based on an analysis of representative video signal bit streams.

12. The method according to claim 10, wherein the prediction is carried out using a prediction model that maps bit rate vs. time based on a second or higher order polynomial to insure smoothness of a bit rate vs. time curve.

13. The method according to claim 11, wherein the encoder algorithm is a JPEG2k algorithm.

14. A method of transmitting a coded video signal in real time via a data network comprising:

encoding a video signal using a compression algorithm having a variable bit rate and a defined plurality of quality levels with corresponding differing bit rates, to provide an encoded data stream;

feeding the encoded data stream to a buffer of known size;

reading data from the buffer via a streamer with a controllable bit rate to provide a bit stream at a desired streaming bit rate for transmission via the network.

monitoring the bit rate (n) of the encoded data signal and predicting a future bit rate (n+1) of the encoded data stream based on the bit rate (n);

defining a set of step-wise constant bit rate streaming levels; and

,

increasing or decreasing the step level of the streaming bit rate (n+1), and thus the streaming bit rate, based on an increase or decrease, respectively, of the predicted encoding bit rate (n+1).

15. The method according to claim 14, enlarging the size of the buffer by a amount equal to the encoding bit rate (n) minus the streaming bit rate (n) when the streaming bit rate is at a maximum level such that further increase in the streaming bit rate would result in a buffer overflow condition.

16. The method according to claim 14, further including defining a relationship between the encoding and streaming bit rates as follows:

encoding bit rate (n)=data input to buffer (n);

data in buffer (n)=data in buffer (n−

1)+encoding bit rate (n)−

streaming bit rate (n);

encoding bit rate (n)=delta (t)+streaming bit rate (t), and

delta (t)=data in buffer (n)−

data in buffer (n−

1).

17. The method according to claim 14, wherein the prediction is carried out using a prediction model that maps bit rate vs. time based on a second or higher order polynomial to insure smoothness of a bit rate vs. time curve.

18. The method according to claim 14, wherein the encoder algorithm is a JPEG2k algorithm.

19. Apparatus for transmitting a coded video image in real time via a data network comprising:

a video encoder for encoding a video image using a compression algorithm having a variable bit rate to provide an encoded data stream;

a buffer of known size connected to receive the encoded data stream;

a streamer with a controllable bit rate connected to the buffer to read data from the buffer and to provide a bit stream at a desired stream bit rate for transmission via the network;

a predictor monitoring the bit rate of the encoded data stream from the encoder and predicting a future bit rate of the encoded data stream; and

,

a control arrangement adjusting the bit rate of at least one of the encoder and the streamer to provide the desired streaming bit rate.

20. The apparatus according to claim 19, wherein the predictor uses a prediction model that maps bit rate vs. time based on a second or higher order polynomial to ensure smoothness of the bit rate vs. time curve.

21. The apparatus according to claim 19, wherein the encoder algorithm is a JPEG2k algorithm.

22. The apparatus according to claim 19, wherein:

a set of strip-wise constant bit rate streaming levels are defined for the streamer; and

the control arrangement raises and lowers the streaming bit rate proportionately to an increase or decrease of the predicted encoded bit rate level, using the set of step-wise streaming levels.

23. The apparatus according to claim 22 wherein the control arrangement enlarges the buffer size by a amount equal to the momentary encoded bit rate minus the momentary streaming bit rate when the streaming bit rate is set to a maximum value such that further increase would result in a buffer overflow condition.

24. The apparatus according to claim 22 wherein the control arrangement maintains the following defined relationship between the encoding and streaming bit rates:

Encoding bit rate (n)=data input to buffer (n);

Data in buffer (n)=data in buffer (n−

1)+encoding bit rate (n)−

streaming bit rate (n);

Encoding bit rate (n)=delta (n)+streaming bit rate (n); and

delta (n)=data in buffer (n)−

data in buffer (n−

1)

25. The apparatus according to claim 19, wherein:

the encoding algorithm includes a defined set of quality levels proportional to the encoding bit rate; and

the control arrangement decreases the encoding quality level and thus the encoding bit rate, if the predicted encoding bit rate is greater than a maximum streaming bit rate level.

26. The apparatus according to claim 25, wherein:

the control arrangement increases the encoding quality level, and thus the encoding bit rate, if the predicted encoding bit rate plus a given threshold value is less than the maximum streaming bit rate level, where the threshold value is an empirical number based on an analysis of representative video streams.

27. The apparatus according to claim 19, wherein the encoding algorithm includes a defined set of quality levels proportional to the encoding bit rate;

and the control arrangement increases the encoding quality level, and thus the encoding bit rate, if the predicted encoding bit rate plus a given threshold value is less than the maximum streaming bit rate level, where the threshold value is an empirical number based on an analysis of representative video streams.