WO2013087793A1

WO2013087793A1 - Streaming video data having adaptable bit rate

Info

Publication number: WO2013087793A1
Application number: PCT/EP2012/075453
Authority: WO
Inventors: I-Chih Kang
Original assignee: Tp Vision Holding B.V.
Priority date: 2011-12-14
Filing date: 2012-12-13
Publication date: 2013-06-20

Abstract

Video streaming transmitters (10) comprise encoders (1) for receiving first video data having first bit rates and encoding the first video data into second video data having second bit rates, senders (2) for transmitting the second video data via networks (20) to video streaming receivers (30), buffers (3) for buffering the second video data between the encoders (1) and the senders (2), and controllers (4) for controlling the encoders (1) in response to buffer information from the buffers (3) and estimator information from estimations of an available bandwidth in the networks (20). The control of the second bit rates may be an easy way for adjusting the video streaming with respect to network capacity fluctuations. The second bit rates get minimum values for filling degrees of the buffers (3) having gone above first thresholds and get estimated available bandwidth values for the filling degrees having gone below second thresholds and are increased stepwise for the filling degrees having gone below third thresholds.

Description

Streaming video data having adaptable bit rate

FIELD OF THE INVENTION

The invention relates to a video streaming transmitter. The invention further relates to a video streaming system, to a method for video streaming, to a method for controlling a video streaming transmitter, to a computer program product and to a storage medium.

Examples of such a video streaming transmitter are televisions, set top boxes, digital versatile disk players / recorders and personal computers.

BACKGROUND OF THE INVENTION

US 2007 / 0053446 Al discloses a system and method for automatic adjustment of a streaming video bit rate. The transmitter comprises a buffer and comprises a buffer monitor for detecting conditions at the buffer. Upon a repeated condition, an encoded bit rate is adjusted higher or lower.

SUMMARY OF THE INVENTION

It is an object of the invention to provide an improved video streaming transmitter. Further objects of the invention are to provide an improved video streaming system, an improved method for video streaming, and an improved method for controlling a video streaming transmitter and a computer program product and a storage medium.

According to a first aspect, a video streaming transmitter is provided comprising

an encoder adapted to receive first video data having a first bit rate and to encode the first video data into second video data having a second bit rate,

a sender adapted to transmit the second video data via a network to a video streaming receiver,

a buffer adapted to buffer the second video data between the encoder and the sender, and a controller adapted to control the encoder in response to buffer information from the buffer and in response to estimator information from an estimation of an available bandwidth in the network.

The encoder receives the first video data having a first bit rate and encodes the first video data into the second video data having the second bit rate. The sender transmits the second video data via the network to the video streaming receiver. The buffer for example comprises a first-in- first-out buffer for buffering the second video data between the encoder and the sender. The controller controls the encoder in response to the buffer information from the buffer and in response to the estimator information from the estimation of the available bandwidth in the network.

As a result, in the video streaming transmitter, said encoding is performed not just in dependence of the buffer information coming from the buffer but also in dependence of the estimator information coming from the estimation of the available bandwidth in the network. This way, said encoding is performed while also taking into account the available bandwidth in the network, and this is a great improvement, compared to when not taking into account the available bandwidth in the network.

An example of an estimation of an available bandwidth of a network is a time interval based bandwidth estimation technique, as disclosed in the article "Bandwidth estimation schemes for a transmission control protocol over wireless networks" by Antonio Capone, Luigi Fratta, and Fabio Martignon, from IEEE Transactions on mobile computing, vol. 3, no. 2, April - June 2004, pages 1-15. Other estimations are common in the art and are not to be excluded. US 7418037 and US 6088360 disclose prior art encoders.

The encoder that receives the first video data having the first bit rate may be an encoder adapted to encode first video data in the form of uncompressed video that has a bit rate which is determined by a number of pixels in video frames. For instance, for a full High Definition video of 1920x1080 pixels at 25 frames per second with 24 bits/pixel, a bit rate of 1244 Mb/s is used, whereas a compressed bit rate, after encoding according to H.264, will be around 12 Mb/s. Other values are not to be excluded. Possibly, the encoder may be a transcoder that transcodes first video data having a first bit rate such as for example already compressed video data into second video data having a second bit rate etc.

An embodiment of the video streaming transmitter is defined by the control of the encoder comprising a control of the second bit rate. The control of the second bit rate is an easy way for adjusting the video streaming with respect to network capacity fluctuations. An embodiment of the video streaming transmitter is defined by the control of the second bit rate comprising setting the second bit rate to a minimum value for a filling degree of the buffer or a manipulation thereof having reached and/or gone above a first threshold. The minimum value may be defined by the encoder or may be defined otherwise. The filling degree or fullness of the buffer as provided via the buffer information may be directly compared with the first threshold, alternatively a manipulation of the filling degree or fullness of the buffer may be compared with the first threshold. Such a manipulation may be a calculation or a process or a conversion or a weighting etc., each per time-interval or for several time-intervals etc.

An embodiment of the video streaming transmitter is defined by the control of the second bit rate comprising setting the second bit rate to an estimated available bandwidth value or a derivation thereof for a filling degree of the buffer or a manipulation thereof having reached and/or gone below a second threshold. The second bit rate can be set to the estimated available bandwidth value as provided via the estimator information or can be set to a derivation thereof, such as a calculation or a process or a conversion or a weighting per time-interval or for several time-intervals. To be on the safe side, the second bit rate may be set to a fraction of the estimated available bandwidth value, such as for example 80% or 90% or 95% etc. The filling degree or fullness of the buffer as provided via the buffer information may be directly compared with the second threshold, alternatively a manipulation of the filling degree or fullness of the buffer may be compared with the second threshold. Such a manipulation may be a calculation or a process or a conversion or a weighting etc., each per time-interval or for several time-intervals etc.

An embodiment of the video streaming transmitter is defined by the control of the second bit rate comprising increasing the second bit rate stepwise for a filling degree of the buffer or a manipulation thereof having reached and/or gone below a third threshold. The filling degree or fullness of the buffer as provided via the buffer information may be directly compared with the third threshold, alternatively a manipulation of the filling degree or fullness of the buffer may be compared with the third threshold. Such a manipulation may be a calculation or a process or a conversion or a weighting etc., each per time-interval or for several time-intervals etc. Especially in this case, the manipulation may be a determination of a running average value of the filling degree or fullness of the buffer, which running average value should stay below the third threshold for a particular number of time-intervals or a particular amount of time. Other average values and other kinds of determinations are not to be excluded. The stepwise increase of the second bit rate here comprises a linear increase with a fixed step size per fixed time-interval or fixed amount of time or an exponential increase with either a increasing step size per fixed time-interval or fixed amount of time or a fixed step size per decreasing time-interval or decreasing amount of time etc. An amount of time may here be equal to a time-interval or not.

An embodiment of the video streaming transmitter is defined by the first threshold being higher than the second and third thresholds, and the third threshold being lower than the first and second thresholds. The first threshold is a relatively high threshold, and the third threshold is a relatively low threshold. The second threshold will be somewhere in between.

An embodiment of the video streaming transmitter is defined by the encoder being adapted to encode the first video data into the second video data relatively

dynamically. A relatively dynamic encoder will react relatively quickly.

An embodiment of the video streaming transmitter is defined by the controller being adapted to control the encoder in response to the buffer information and in response to the estimator information per time-interval. This time-interval may be a fixed time-interval or a flexible time-interval.

An embodiment of the video streaming transmitter is defined by further comprising

- an estimator adapted to provide the estimator information in response to the buffer information from the buffer.

Generally, the controller does not perform a manipulation or performs a first, relatively simple manipulation of the filling degree or fullness of the buffer as provided via the buffer information, where the estimator may perform a second, relatively complex manipulation of the filling degree or fullness of the buffer as provided via the buffer information. The estimator may form part of the controller or may be connected to the controller.

An embodiment of the video streaming transmitter is defined by the video streaming transmitter and the network and the video streaming receiver being compliant with a hyper text transfer protocol. Via the hyper text transfer protocol, at a relatively high level there is no acknowledgement of receipt, only at a relatively low level there is

acknowledgement of receipt. Should there be acknowledgement of receipt at the relatively high level, then this procedure could be used for controlling the encoder. Other protocols not having acknowledgement of receipt at the relatively high level are not to be excluded. According to a second aspect, a video streaming system is provided comprising the video streaming transmitter as defined above and further comprising the video streaming receiver.

According to a third aspect, a method is provided for video streaming transmission comprising the steps of

receiving first video data having a first bit rate,

encoding the first video data into second video data having a second bit rate, transmitting the second video data via a network to a video streaming receiver, buffering the second video data between the receiving step and the sending step, and

controlling the encoding step in response to buffer information from the buffering step and in response to estimator information from an estimation of an available bandwidth in the network.

According to a fourth aspect, a method is provided for controlling a video streaming transmitter comprising an encoder adapted to receive first video data having a first bit rate and to encode the first video data into second video data having a second bit rate, a sender adapted to transmit the second video data via a network to a video streaming receiver, and a buffer adapted to buffer the second video data between the encoder and the sender, the method comprising a step of

controlling the encoder in response to buffer information from the buffer and in response to estimator information from an estimation of an available bandwidth in the network.

According to a fifth aspect, a computer program product is provided adapted to perform when being run on a computer the step of the method as defined above.

According to a sixth aspect, a storage medium is provided comprising the computer program product as defined above.

An insight is that a control based on one kind of information is relatively non- objective. A basic idea is that a control is to be based on at least two kinds of information - buffer information from a buffer and estimator information from an estimation of an available bandwidth in the network.

A problem to provide an improved video streaming transmitter has been solved. A further advantage is that the network can be used more efficiently.

These and other aspects of the invention will be apparent from and elucidated with reference to the embodiments described hereinafter. BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

Fig. 1 shows a first embodiment of a video streaming transmitter, a network and a video streaming receiver, and

Fig. 2 shows a second embodiment of a video streaming transmitter, a network and a video streaming receiver.

DETAILED DESCRIPTION OF EMBODIMENTS

In the Fig. 1, a first embodiment of a video streaming transmitter 10 is shown, coupled via a network 20 to a video streaming receiver 30. The video streaming transmitter 10 comprises an encoder 1 adapted to receive first video data having a first bit rate from a memory or a cable network or a satellite network etc. and adapted to encode the first video data into second video data having a second bit rate. The video streaming transmitter 10 further comprises a sender 2 adapted to transmit the second video data via a network 20 to a video streaming receiver 30. The network 20 will usually be a wireless network that experiences network capacity fluctuations, but other kinds of networks experiencing such network capacity fluctuations are not to be excluded.

The video streaming transmitter 10 further comprises a buffer 3 adapted to buffer the second video data between the encoder 1 and the sender 2. The video streaming transmitter 10 further comprises a controller 4 coupled to the buffer 3 for receiving buffer information. The controller 4 is adapted to control the encoder 1 in response to the buffer information from the buffer 3 and in response to estimator information from an estimation of an available bandwidth in the network 20. Here, said estimator information is provided by an estimator 5 located outside the controller 4 and also coupled to the buffer 3 for receiving the buffer information.

Preferably, the control of the encoder 1 as performed by the controller 4 comprises a control of the second bit rate. In other words, the controller 4 controls the encoder 1 to adjust the second bit rate of the video data.

The control of the second bit rate may comprise setting the second bit rate to a minimum value for a filling degree of the buffer 3 or a manipulation thereof having reached and/or gone above a first threshold. In other words, in case the buffer 3 gets relatively full (bandwidth drop in the network 20), the encoder 1 is controlled to provide video data at the second bit rate equal to the minimum value, to prevent that the buffer 3 will get too full. The control of the second bit rate may comprise setting the second bit rate to an estimated available bandwidth value or a derivation thereof for a filling degree of the buffer 3 or a manipulation thereof having reached and/or gone below a second threshold. In other words, as soon as a filling degree or fullness of the buffer has been reduced sufficiently, the encoder 1 is controlled to provide video data at the second bit rate equal to the estimated available bandwidth value or a smaller value y derived from the estimated available bandwidth value (80%<y<100%, preferably 90%<y<100%, further preferably

95%<y<100%), to be on the safe side.

The control of the second bit rate may comprise increasing the second bit rate stepwise for a filling degree of the buffer 3 or a manipulation thereof having reached and/or gone below a third threshold. In other words, in case the buffer 3 gets relatively empty, the encoder 1 is controlled to provide video data at the second bit rate that is increased stepwise until it has reached a maximum value that may be equal to the first bit rate or an original content bit rate value or until the first threshold is reached.

Preferably, the first threshold may be higher than the second and third thresholds, and the third threshold may be lower than the first and second thresholds. Further, preferably, the encoder 1 may be adapted to encode the first video data into the second video data relatively dynamically. Further, preferably, the controller 4 may be adapted to control the encoder 1 in response to the buffer information and in response to the estimator information per time-interval. Further, preferably, the video streaming transmitter 10 and the network 20 and the video streaming receiver 30 may be compliant with a hyper text transfer protocol.

Each manipulation may be a calculation or a process or a conversion or a weighting etc., each per time-interval or for several time-intervals etc. Especially for the case wherein the filling degree or fullness of the buffer 3 or a manipulation thereof has reached and/or gone below a third threshold, the manipulation may be a determination of a running average value of the filling degree or fullness of the buffer, which running average value should stay below the third threshold for a particular number of time-intervals or a particular amount of time. But other average values and other kinds of determinations are not to be excluded. The manipulation also allows the filling degree or fullness of the buffer 3 to have a relative value and to have an absolute value.

In the Fig. 2, a second embodiment of a video streaming transmitter 10 is shown, coupled via a network 20 to a video streaming receiver 30. The only difference with the first embodiment is that here the estimator 5 forms part of the controller 4. Summarizing, video streaming transmitters 10 comprise encoders 1 for receiving first video data having first bit rates and encoding the first video data into second video data having second bit rates, senders 2 for transmitting the second video data via networks 20 to video streaming receivers 30, buffers 3 for buffering the second video data between the encoders 1 and the senders 2, and controllers 4 for controlling the encoders 1 in response to buffer information from the buffers 3 and estimator information from estimations of an available bandwidth in the networks 20. The control of the second bit rates may be an easy way for adjusting the video streaming with respect to network capacity fluctuations. The second bit rates get minimum values for filling degrees of the buffers 3 having gone above first thresholds and get estimated available bandwidth values for the filling degrees having gone below second thresholds and are increased stepwise for the filling degrees having gone below third thresholds.

While the invention has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive; the invention is not limited to the disclosed embodiments. Other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. Any reference signs in the claims should not be construed as limiting the scope.

Claims

CLAIMS:

1. A video streaming transmitter (10) comprising

an encoder (1) adapted to receive first video data having a first bit rate and to encode the first video data into second video data having a second bit rate,

a sender (2) adapted to transmit the second video data via a network (20) to a video streaming receiver (30),

a buffer (3) adapted to buffer the second video data between the encoder (1) and the sender (2), and

a controller (4) adapted to control the encoder (1) in response to buffer information from the buffer (3) and in response to estimator information from an estimation of an available bandwidth in the network (20).

2. The video streaming transmitter (10) as defined in claim 1, the control of the encoder (1) comprising a control of the second bit rate.

3. The video streaming transmitter (10) as defined in claim 2, the control of the second bit rate comprising setting the second bit rate to a minimum value for a filling degree of the buffer (3) or a manipulation thereof having reached and/or gone above a first threshold.

4. The video streaming transmitter (10) as defined in claim 3, the control of the second bit rate comprising setting the second bit rate to an estimated available bandwidth value or a derivation thereof for a filling degree of the buffer (3) or a manipulation thereof having reached and/or gone below a second threshold.

5. The video streaming transmitter (10) as defined in claim 4, the control of the second bit rate comprising increasing the second bit rate stepwise for a filling degree of the buffer (3) or a manipulation thereof having reached and/or gone below a third threshold.

6. The video streaming transmitter (10) as defined in claim 5, the first threshold being higher than the second and third thresholds, and the third threshold being lower than the first and second thresholds.

7. The video streaming transmitter (10) as defined in claim 1, the encoder (1) being adapted to encode the first video data into the second video data relatively

dynamically.

8. The video streaming transmitter (10) as defined in claim 1, the controller (4) being adapted to control the encoder (1) in response to the buffer information and in response to the estimator information per time-interval.

9. The video streaming transmitter (10) as defined in claim 1, further comprising an estimator (5) adapted to provide the estimator information in response to the buffer information from the buffer (3).

10. The video streaming transmitter (10) as defined in claim 1, the video streaming transmitter (10) and the network (20) and the video streaming receiver (30) being compliant with a hyper text transfer protocol.

11. A video streaming system comprising the video streaming transmitter (10) as defined in claim 1 and further comprising the video streaming receiver (30).

12. A method for video streaming transmission comprising the steps of

- receiving first video data having a first bit rate,

encoding the first video data into second video data having a second bit rate, transmitting the second video data via a network (20) to a video streaming receiver (30),

buffering the second video data between the receiving step and the sending step, and

13. A method for controlling a video streaming transmitter (10) comprising an encoder (1) adapted to receive first video data having a first bit rate and to encode the first video data into second video data having a second bit rate, a sender (2) adapted to transmit the second video data via a network (20) to a video streaming receiver (30), and a buffer (3) adapted to buffer the second video data between the encoder (1) and the sender (2), the method comprising a step of

controlling the encoder (1) in response to buffer information from the buffer (3) and in response to estimator information from an estimation of an available bandwidth in the network (20).

14. A computer program product adapted to perform when being run on a computer the step of the method as defined in claim 13.

A storage medium comprising the computer program product as defined