Code rate smoothing method of video live transmission through wireless network

A real-time transmission and wireless network technology, applied in transmission system, wireless communication, network traffic/resource management, etc., to achieve the effect of solving video freeze, improving fluency, and saving storage space

Inactive Publication Date: 2014-07-09

BEIJING XINWEI TELECOM TECH +1

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AI-Extracted Technical Summary

Problems solved by technology

[0004] In order to solve the problem of not only ensuring the real-time performance of video transmission, but also improving its transmission quality and ensuring its fluency as much as possible, the present invention proposes a bit rate smoothing method for real-time video transmission under wireless network, based on the play cache mechanism On the one hand, by periodically counting the transmission delay of video frames to dynamic...

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Method used

The present embodiment can smooth the variation of 1 frame transmission time delay by dynamically adjusting the size of the buffer, and when the time delay can be satisfied, inc...

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Abstract

The invention provides a code rate smoothing method of video live transmission through wireless network. The method comprises the steps that the periodic statistics of transmission delay of video frames is conducted, when the transmission delay gets smaller, playing buffer is turned down through playing speeding up, when the transmission delay gets bigger, the playing buffer is turned up through playing slowing down, and the adjusting step length of the playing speeding up and the adjusting step of the playing slowing down are codetermined by changing of the transmission delay, the playing buffer depth and timestamp information. By means of the code rate smoothing method of video live transmission through wireless network, the statistics of the transmission delay of the video frames can be conducted, the wireless network state is perceived according to time delay information, the minimum video time delay is further found out according to the actual network condition to achieve the smooth effect, and balance between real-time performance and fluency performance of video streaming is achieved.

Application Domain

Network traffic/resource managementTransmission +1

Technology Topic

Transmission delayTimestamp +8

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Examples

Experimental program(1)

Example Embodiment

[0015] The present invention will be further described in detail through specific embodiments below in conjunction with the accompanying drawings.

[0016] This embodiment takes the I frame smoothing of video real-time transmission under the wireless network as an example. In this embodiment, communication device A performs real-time video transmission to communication device B, and processes it at the receiving end device B. The specific process is:

[0017] (1) Communication device A packs and sends the collected and coded code stream, and each package carries the time stamp information of each frame;

[0018] (2) The communication device B starts receiving, initializes the playback buffer, and counts the transmission delay D of each I frame i , reorder the received packets, and then decode them, such as figure 1 shown;

[0019] (3) Use the ring buffer to store the decoded video frames. The frames that have just been decoded and need to be buffered enter from the tail, and the pointer is tail. The frames to be played are output from the head of the ring buffer, and the pointer is head. After a frame is decoded, first judge whether the buffer is full, if it is full, the tail pointer remains unchanged, and the frame cannot be stored, otherwise the frame is put into the buffer, and the pointer to the frame is set as tail;

[0020] (4) Set a sliding window with a size of time T, which is used to weight the average transmission delay of each I frame within the latest T time to obtain a delay value of a i (i=1, 2, . . . , N) are weighting factors.

[0021] (5) Set the start playback threshold. When the number of frames in the cache reaches the threshold for the first time, the display starts, and the local time T when the first frame is displayed is recorded at the same time. local_base and the sending timestamp T of the first frame ts_base , based on this, control the display time of subsequent frames.

[0022] (6) The adjustment period of fast forward and slow playback can be set, the minimum is one video frame interval. In this embodiment, the adjustment cycle of fast-forward and slow-play is set to T1, and the transmission delay value in the sliding window is counted every T1 time, and the weighted delay value D calculated by this adjustment cycle is used. curr Compared with the weighted delay value D of the previous adjustment cycle statistics last To estimate the state of the wireless network before the next adjustment period. compare current moment D curr value and the previous cycle's D last value, if the former is larger, it means that the I frame delay becomes larger, and the network tends to deteriorate, so it is necessary to dynamically increase the playback buffer to cope with large fluctuations in the network; if the latter is larger, it means that the network is getting better Trend, so the playback cache can be dynamically reduced to minimize the cache delay.

[0023] (7) Fast-forward and slow-play adjustments are made every T1 time, and the playback buffer is increased or decreased through small-grained slow-play or fast-forward. Depth and timestamp information are jointly determined. In this embodiment, by adjusting the local time T when the first frame is displayed local_baseTo adjust the playback interval of each frame, that is, each frame is adjusted as follows when slowing down: T local_base_new = T local_base +0.25pq slow ·ΔT ts , each frame is adjusted as follows during fast playback: T local_base_new = T local_base -0.25pq fast ·ΔT ts. in, p = | D curr - D last D last | , | D curr - D last | D last 1 , | D curr - D last | ≥ D last ; To reflect the factor of I frame transmission delay variation; A factor reflecting the cache depth during slow playback; is the factor reflecting the cache depth during fast playback; ΔT ts It is the playback interval between two adjacent frames when playing according to the timestamp.

[0024] (8) Perform display judgment. like figure 2 As shown, a timer is set in the display thread, and the display time is regularly queried. Calculated in each timing cycle: the current time and the local time T when the first frame is displayed after the fast-forward and slow-motion adjustment local_base_new The difference Δt of , and the difference Δts between the sending timestamp of the current frame and the timestamp of the first frame, when Δt>Δts, the frame is displayed, and the pointer of the next frame is set to head.

[0025] It needs to be explained: 1. The timing interval setting of the timer needs to be smaller than the interval between the time stamps of two adjacent frames. The smaller the timing interval setting, the higher the accuracy of the displayed time, but at the same time, the timer will be woken up in a shorter time for query. display, consumes more CPU resources. 2. Display the reference frame (ie the first frame) is variable. In the case of screen switching, etc., when the cache is empty, the reference frame can be re-set to reduce the cumulative timing error.

[0026] In this embodiment, by dynamically adjusting the size of the cache, the variation of the I-frame transmission delay can be smoothed, and the buffer can be increased when the delay is large to prevent the buffer from emptying, and when the delay is small, the cache can be reduced to reduce the delay. Ensure that the frame can be played faster.

[0027] The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present invention should be included in the protection of the present invention. within range.

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Classification and recommendation of technical efficacy words

Improve fluency
Solve video freeze

Code rate smoothing method of video live transmission through wireless network

A real-time transmission and wireless network technology, applied in transmission system, wireless communication, network traffic/resource management, etc., to achieve the effect of solving video freeze, improving fluency, and saving storage space

AI-Extracted Technical Summary

Problems solved by technology

Method used

Abstract

Image

Examples

Example Embodiment

PUM

Description & Claims & Application Information

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