TWI504245B - A video transmission control method - Google Patents

Description

Video transmission control method

The present invention relates to a video transmission control method, and more particularly to a video transmission control method for determining transmission content by the priority of a data layer of an adjustable video compression standard (H.264/SVC) and the validity of a video packet.

According to the development of wireless communication technologies (such as mobile communication and telematics) and home network devices, home network devices and various wireless communication networks can be seamlessly connected with the Internet ( Seamless) connectivity that greatly expands the range of network services (eg, video streaming services, etc.).

Take the video streaming service as an example, through a client device (Terminal Client), a mobile gateway (Mobile Gateway), a media server (Media Server), and a heterogeneous network (Heterogeneous Network) connected therebetween. The video stream data of the server can be retrieved, for example, video data compressed by an adjustable video compression standard (H.264/SVC). Among them, because the transmission signal between the client and the gateway is susceptible to interference, how to smoothly and seamlessly transmit to the client device for the video stream data with extremely high network bandwidth and stability requirements It is still the goal of the relevant R&D personnel.

Taking H.264/SVC video compression technology as an example, the adaptation method includes three types: spatial Scalability (D), Temporal Scalability (T), and Quality Scalability (Q). As shown in the figure, various adaptation modes can be divided into a base layer (for example, D0, T0 or Q0) and at least one enhancement layer (for example, D1, T1 or Q1, etc.), and the basic layer is only provided. The basic picture quality data, the gain layer provides data for improving the quality of the base layer picture, wherein each base layer or gain layer can be divided into several periods (epoch), and each period can be divided into several groups (Group of Picture) , GOP), each group can be divided into several frames, each frame can be divided into several packets (Packet). Thereby, the encoding and decoding adaptation of the video data can be made more flexible to meet the needs of video streaming.

However, due to the inter-reference of the images of the three adaptation modes, for example, the space, time and quality adjustable coding/decoding reference relationship shown in Figures 2a, 2b and 2c, the video data has more complicated dependencies. During the transmission process, if a network congestion occurs, the video data (eg, Packet) is faulty or lost, which will affect the decoding result of other video data, thereby improving the video. The difficulty of decoding.

In order to solve the above video decoding problem, the video priority control (Video Priority Control) technology has been developed, which can be further divided into Rate-based Video Priority Control and Drop-based Video Priority Control. The methods are as follows:

The above rate control method uses the bandwidth estimation (Bandwidth Estimation) and the congestion control (Congestion Control) technology in the H.264/SVC transmission layer to adjust the video data to be transmitted in real time according to the actual network congestion condition at the receiving end. For Rate Control. However, in the process of adjusting the transmission rate, this method does not consider the impact of packet loss (Secret Lost) on the decoding of subsequent video data, resulting in unresolvable data occupying storage space and limited network bandwidth, which cannot ensure videoconferencing. The validity of data transmission, and may cause buffer overflow (Buffer Overflow) and network congestion.

The above discard control method is based on H.264/SVC adaptation layer information, using traffic splitting (Traffic Splitting) technology and frame-priority-based dropping technology, discarding less important according to the characteristics of video coding. Information to control network traffic and avoid network congestion. However, this method only discards data for time-adjustable dependencies, and does not fully consider the effects of three adjustable dimensions (ie, space, time, and quality), resulting in video decoding with spatial and quality-adjustable dependencies; Moreover, the threshold value (Threshold) in setting the adjustment data is too rough, which may result in excessive data deletion. As a result, the quality of video is seriously degraded.

In summary, the conventional video transmission control method will cause video quality degradation and low transmission efficiency when the network is blocked. In addition, there will be "buffer overflow" and "data congestion" in the transmission process. When used, it has different limitations and shortcomings. It is inconvenient and needs further improvement to improve its practicability.

The object of the present invention is to improve the above-mentioned shortcomings, and to provide a video transmission control method, which can filter the unrepeatable video data by using the three adjustable dimensions of H.264/SVC to improve the validity of data transmission.

A second object of the present invention is to provide a video transmission control method that discards less important video data based on consideration of three adjustable dependencies of H.264/SVC to avoid severe degradation of video quality.

The term "coupling" as used throughout the present invention means that the data of the two devices can be transmitted to each other by means of a wired entity, a wireless medium or a combination thereof (for example, a heterogeneous network). It is understood by those of ordinary skill in the art to which the present invention pertains.

"Coding Dependency" as used throughout the present invention refers to encoded Video Streaming data, depending on time (T), space (D) or quality (frame). Q) Adjustable characteristics, and form a mutual reference property, as shown in Figure 3a, depending on time (T _n , n = 0 to 3), space (D _m , m = 0 to 1) or quality (between frames) Q _k , k = 0 ~ 1) adjustable characteristics and mutual reference, but not limited to this. For example, as shown in Figure 3b, one of the groups contains 8 frames, if the frame's identification code, spatially adjustable, time-adjustable, and quality-adjustable parameters are (i, d, t, respectively). , q) means that i is the frame number, d is the spatially adjustable parameter value, t is the time adjustable parameter value, and q is the spatially adjustable parameter value. Then, when the server 1 performs video encoding, the frame (0, 0, 0, 0) is provided with (0, 0, 0, 1), (0, 1, 0, 0) and (1, 0, 1, 0) As a coding reference, the frame (1,0,1,0) is further supplied with (1,0,1,1) as the coding reference, and the frame (0,1,0,0) is re-supplied (0). , 1,0,1) and (1,1,1,0) as coding references, wherein the frame (1,1,1,0) is further provided with (1,1,1,1) as the coding reference, and the rest Frames can be deduced by analogy. In other words, when decoding each frame, refer to the frame for which it is used as a coding reference. For example, the frame (0, 0, 0, 1) needs to refer to (0, 0, 0, 0), etc., in order to decode smoothly. It will be understood by those of ordinary skill in the art to which the present invention pertains.

A video transmission control method includes: a setting program, wherein a server divides a frame of a different stream of data into a plurality of packets, and then sets each packet according to a group priority, and then transmits The packet is sent to a gateway, and the gateway temporarily stores the packet from the server; and an adjustment procedure is determined by the gateway according to the temporary storage capacity of the packet to determine whether to discard the lower priority. The packet is further determined whether each packet belongs to the same group. If the determination is yes, the packets are regarded as valid or invalid according to the coding dependency between the frames. If the determination is no, the transmission is regarded as valid. The packet is packaged to a client; wherein the adjustment procedure includes: a discarding step, wherein the gateway determines whether the temporary storage capacity of the packet is higher than a threshold upper limit, and if the determination is yes, discarding the temporary storage If the priority of the packet is the lowest, if the judgment is no, the packet from the server is continuously received; in a determining step, it is determined by the gateway whether the temporarily stored packets belong to the same group, and if the determination is yes, Carry out one Packet filtering operation, if the determination is no, a packet transmission operation is performed; in a filtering step, the packet filtering operation is performed by the gateway, and each frame itself and its reference are judged according to the coding dependency between the frames. Whether the packet of the frame has been collected. If the judgment is yes, the packet of the frame itself is regarded as valid. If the determination is no, the packet of the frame itself is regarded as invalid; and a transmission step The packet transmission operation is performed by the gateway, and the packet deemed to be invalid is discarded, and the packet deemed to be valid is transmitted to the client.

The method further includes a recombination program, wherein the client forms a valid packet into the frame, and trims the frame that cannot be decoded according to the coding dependency between the frames.

Wherein, the discarding step, and then the gateway determines that the temporary storage capacity is No higher than the lower threshold of a gateway. If the judgment is yes, the current temporary storage capacity is maintained. If the determination is negative, the packet from the server is continuously received, wherein the lower threshold of the gateway is lower than the gateway. Limit.

The server sequentially sets the priority of the packet from high to low according to one of the time, a space and a quality adjustable parameter of the stream data.

The above and other objects, features and advantages of the present invention will become more <RTIgt;

Referring to FIG. 4, it is a system architecture diagram of a preferred embodiment of the video transmission control method of the present invention, wherein a gateway (Mobile Gateway) 2 is coupled to a client (Terminal Client) 3 and a servo. (Media Server) 1. The server 1 can be selected as a media server (Media Server) with data storage function, etc., for parsing streaming (Streaming) data formats (eg, video frames), and packing streaming data. It is a number of packets (for example, Video Streaming Packet), sets the priority of each packet, and transmits the packet to the gateway 2. The gateway 2 can be selected as a mobile gateway with a data storage function, etc., for temporarily storing the packet transmitted by the server 1 and transmitting a valid packet to the client 3, wherein the gate 3 The tracker 2 can drop the lower priority packet in time according to whether the temporary storage capacity of the packet exceeds the temporary storage limit, and the gateway 2 according to the coding dependency between the packets (Coding) Dependency) Filters packets that cannot be decoded (that is, packets that are considered invalid) to avoid buffer overflow (Buffer Overflow) or invalid packets occupying network bandwidth. The client 3 can be selected as a portable device with a data storage function, etc., for reassembling the decodable packet (ie, the packet deemed to be valid) into the frame data, and according to the above coding. Dependency Trimming cannot decode the frame data for frame decoding. Thereby, the user can retrieve the streaming data of the server 1 through the client 3 and the gateway 2. In this embodiment, the streaming data is implemented in an adjustable video compression standard (H.264/SVC), and other video data having both time, space, and quality characteristics can be selected. There are no limits.

Referring to FIG. 5, it is an operational flowchart of a preferred embodiment of the video transmission control method of the present invention, wherein the video transmission control method includes a setting program S1 and an adjustment program S2.

In the setting program S1, the server 1 divides the frames of different groups of a stream of data into several packets, and after each packet is set according to the priority of the group, the packet is transmitted to the gateway. 2. The packet from the server 1 is temporarily stored by the gateway 2. In detail, when the user wants to watch the multimedia stream by the client 3, the client 3 can transmit a request message to the server 1 through the gateway 2, for example, requesting a certain stream of data. The message, after the server 1 receives the request message, divides the stream data requested by the client 3 into different groups according to different H.264/SVC video data layers (for example: epoch1) 2, 3, ..., n), and then package the frames of each group into several packets, for example: video information (Video Packets such as Information), Video Data, and Control Massage are temporarily stored in the server 1. To facilitate subsequent procedures, each packet can be regarded as an invalid packet. The server 1 sets the priority of each packet according to the time (T), space (D) and quality (Q) adjustable parameters of each group to which the packet belongs, if the packet needs to be discarded, First discard the data with low priority (that is, the packet with less reference time), and retain the more important data (that is, the packet with more reference times). In this embodiment, the server 1 is based on one of the stream data (T), a space (D), and a quality (Q) adjustable parameter from small (representing the base layer) to large (representing the gain). Layer), and set the priority from high to low. For example, as shown in the following list 1, when the time, space, and quality adjustable parameters are 0~3, 0~1, and 0~1, the priority of the video data packet with different adjustable parameters can be set. Priority is given to 1st to 16th.

Wherein, if the time (T), space (D), and quality (Q) adjustable parameters of the video data packet are 0, 0, and 0, respectively, the highest priority (ie, the first priority); if the video data packet is included The time (T), space (D), and quality (Q) tunable values of 3, 1, and 1, have the lowest priority (ie, the 16th priority), and the remaining time, space, and quality tunable parameters represent Priority can be deduced by analogy.

Then, when the number of temporarily stored packets exceeds a servo upper limit (for example, 300), the server 1 will start transmitting the packet to the gateway 2, and the gateway 2 receives the packet. After that, the packet is temporarily stored, and video information such as the amount of packets transmitted per second is set according to the video information packet, and then the gateway device 2 presets the received packet status as an invalid packet, and Record the group to which each packet belongs (for example: epoch) for subsequent evaluation of the validity of the packet.

In the adjustment program S2, the gateway device 2 determines whether to discard the packets with lower priority according to the temporary storage capacity of the packet, and then determines whether the packets belong to the same group. If the determination is yes, According to the frame The encoding dependency treats each packet as valid or invalid; if the determination is "No", only the packet deemed to be valid is transmitted to the client 3. Then, the setting step S1 is performed again. The adjustment procedure S2 includes a discarding step S21, a judging step S22, a filtering step S23, and a transmitting step S24, respectively, as follows:

In the step S21, the gateway 2 determines whether the temporary storage capacity of the packet is higher than a threshold of the gateway. If the determination is YES, the lowest priority among the temporarily stored packets is discarded; If no, the packet from the server 1 continues to be received. In detail, when the gateway 2 temporarily stores the packet from the server 1, if the temporary storage capacity of the packet is higher than the upper threshold of the gateway (for example, 80% of the maximum temporary storage amount), a part of the packet must be discarded. The temporarily stored packet is preferably discarded after the packet of the lower priority video data layer, so that the temporary storage capacity is lower than the upper threshold of the gateway to avoid buffer overflow (Buffer Overflow), wherein Packets are part of the lower priority video data layer (ie, less important decoding reference material) to avoid severe degradation in video quality.

In addition, the gateway device 2 can further determine whether the temporary storage capacity is higher than a lower threshold value (for example, 20% of the maximum temporary storage amount), and the lower threshold value of the gateway is lower than the upper limit value of the gateway. If it is "Yes" (that is, between the upper threshold of the gateway and the lower limit of the gateway), the current temporary storage capacity can be maintained; if the determination is "No", the packet from the server 1 can continue to be received. For example, a packet of another video data layer.

In the determining step S22, the gateway 2 determines whether the temporarily stored packets belong to the same group. If the determination is YES, the filtering step S23 is performed to perform a packet filtering operation; if the determination is "No" Then, do this Step S24 is transmitted to perform a packet transfer operation. In detail, since the server 1 sequentially packs the frames of different groups into a plurality of packets and transmits them to the gateway 2, the frame is prevented from being excessively stored in the gateway 2 When the coding dependency determines whether the packet is valid, it may be based only on the packet of the same group (for example, epoch 1, 2, 3, etc.), when the gateway 2 temporarily stores the current group (for example: epoch1) If a packet belonging to the next group (for example: epoch2) is received, the invalid packet of the current group (for example: epoch1) can be discarded, and the packet that the current group is regarded as valid is transmitted to the client. End 3 to avoid a buffer overflow situation.

In the filtering step S23, the packet filtering operation is performed by the gateway device 2, and according to the coding dependencies between the frames, it is determined whether the frames of the frame itself and the reference frame of the frame are all collected, and if the judgment is “ Yes, the packet of the frame itself is considered to be valid. If the judgment is "No", the packet of the frame itself is regarded as invalid. In detail, when the server 1 (ie, the encoding end) divides the frames into a plurality of packets for transmission, the client 3 (ie, due to factors such as the size, number, and arrival time of the packets of each frame) When the decoding end decodes the image according to the coding dependency between the frames, the frame itself and the reference packet of the frame itself are collected, and then the frame itself or its reference frame is being decoded. If the packet is not collected (for example, lost, etc.), the frame cannot be decoded normally. Therefore, when the frame received by the gateway 2 and the reference packet thereof have been collected, the packet of the frame itself is regarded as invalid by the invalid tampering, and only the transmission is regarded as 〝 Valid packets to the client 3 can prevent invalid data from occupying limited network resources. An example is as follows:

Please refer to FIG. 6a, which is a schematic diagram (1) of packet transmission control of the gateway device of the present invention, wherein when the gateway device 2 receives the packet transmitted by the server 1, it will judge each frame. Whether the associated packet is collected or not, if the frame itself and the reference frame of the frame are collected, the gateway 2 will treat the packet of the frame as valid (as shown in the figure) Packet 〞V), for example: packet (0,0,0,0), (0,0,0,1), (1,0,1,0) and (1,0,1,1) Otherwise, the packet of the frame is still invalid (as shown in the figure, invalid packet 〞I), for example: frame (0,1,0,0), (0,1,0,1) , (1,1,1,0) and (1,1,1,1) packets, where the frame (0,1,0,0) and (1,1,1,1) are their own packets In the case of uncollected, the frames (0, 1, 0, 1) and (1, 1, 1, 0) are the unpacked packets of their reference frame. Wherein, when the gateway device 2 determines whether the packet to which each frame belongs is collected, the packet is still received. Therefore, after the gateway device 2 filters out the valid packet, it can be checked again and is invalid. Whether the 封 packet (ie 〝 invalid packet 〞 I) can be changed to be valid (ie, valid packet 〞V).

Please refer to FIG. 6b, which is a schematic diagram of packet transmission control of the gateway device of the present invention (2), wherein the frame (0, 1, 0, 0) itself and its reference frame (0, 0) The packets of 0,0) have been collected, and the frame (0,1,0,1) and (1,1,1,0) themselves and their reference frames (0,1,0,0) The packets have been collected, so they are all considered to be valid (ie, valid packets 〞V).

In the transmitting step S24, the packet transfer operation is performed by the gateway device 2, and the packet regarded as invalid is discarded, and the packet regarded as valid is transmitted to the client 3. In detail, when the gateway 2 receives the packet of the next group (for example, epoch2), the packet filtering and viewing operation of the current group (for example, epoch1) must be ended. If there is a packet belonging to the frame of the current group, the packet is still not collected (that is, the packet of the frame is considered invalid), for example, the frame (1, 1, 1, 1) shown in Figure 6b, Then, the gateway 2 considers that the unpacked packet has been lost, and discards the entire frame (ie, is emptied from the temporary storage space), for example, the frame shown in Figure 6c (1, 1, 1,1). Next, the gateway 2 transmits the packets (ie, the valid packets 〞V) that are considered to be valid in the current group to the client 3. Therefore, by the gateway device 2 filtering the video stream data that cannot be normally decoded (ie, the invalid packet), the transmission amount of the invalid data can be reduced, thereby improving the transmission efficiency. Thereafter, the setting step S1 is performed again, and the gateway 2 continuously receives other packets from the server and determines whether it is valid or invalid.

In addition, the video transmission control method of the present invention may further comprise a reassembly procedure S3, wherein the client 3 constructs the frame by the valid packet, and trims the frame that cannot be decoded according to the coding dependency between the frames. In detail, since the invalid data (ie, the invalid packet 传输) transmitted between the server 1 and the gateway 2 has been filtered by the code dependency between the frames of the gateway 2, the After receiving the packet from the gateway 2 and temporarily storing it, the client 3 may trim the frame that cannot be decoded according to the coding dependency between the frames, that is, according to the coding dependency between the frames, the decoding cannot be decoded. The frame is discarded, and the decodable frame is converted into an image, and the frame that can be decoded is preferably copied to fill the frame that cannot be decoded, so as to improve the smoothness of the user when watching the video stream.

In summary, if the Harry Potter trailer (taken from http://minarlab.mis.npust.edu.tw/AMVS) is used as the test film, and the JSVM 9.15 reference software is used to encode H.264/SVC. format. film Detailed configuration information for the encoding parameters is shown in Table 2 below.

Please refer to FIG. 7, which is a schematic diagram of test results of a preferred embodiment of the video transmission control method of the present invention, wherein a high peak noise ratio (PSNR) can be maintained at different bit rates. Value, therefore, under limited network transmission bandwidth, not only can the image be transmitted efficiently, but also a certain image quality can be maintained.

The main features of the video transmission control method disclosed by the present invention are as follows: The gateway device 2 can determine whether the temporary storage capacity of the packet is higher than the upper limit of the gateway, and if it is determined to be "Yes" Then, the lowest priority among the temporarily stored packets is discarded. If the determination is No, the packet from the server 1 is continuously received; and the gateway 2 determines whether the temporarily stored packets belong to the same group. Group, if the judgment is "Yes", the packet is made If the filtering operation is negative, the packet transmission operation is performed. The packet filtering operation is performed by the gateway device 2, and the valid packet is filtered by the invalid packet that is not discarded according to the coding dependency between the frames. And checking whether there is still a valid packet in all the temporarily stored packets; the packet transmission operation is discarded by the gateway 2 to invalidate the group, and then the valid packet of the group is transmitted to the client 3. Therefore, the video transmission control method of the present invention firstly filters the video data that cannot be decoded by the dependency of three adjustable dimensions of H.264/SVC, thereby improving the effectiveness of data transmission and improving the smoothness of the user watching the video. The efficacy of the invention.

Furthermore, the server 1 is based on the time, space and quality adjustable parameters of the stream data from small to large (that is, according to the time adjustable parameter from small to large, and then according to the spatially adjustable parameters from small to large , according to the quality adjustable parameter from small to large), and set the priority of the packet from high to low, if the gateway 2 determines that the temporary storage capacity of the packet is higher than the upper limit of a gateway, you can abandon the temporary The lowest priority among the stored packets is such that the temporary storage capacity is lower than the upper threshold of the gateway to avoid buffer overflow, since the discarded packet belongs to the lower priority video data layer (ie, the less important decoding reference) Data), can avoid serious degradation of video quality. Therefore, the video transmission control method of the present invention is based on the consideration of three adjustable dependencies of H.264/SVC, and discarding less important video data can avoid serious degradation of video quality and improve the clarity of the user watching the video. The efficacy of the invention.

While the invention has been described in connection with the preferred embodiments described above, it is not intended to limit the scope of the invention. The technical scope of the invention is protected, and therefore the scope of protection of the present invention is attached The scope of the patent application is subject to change.

〔this invention〕

1‧‧‧Server

2‧‧‧ gateway

3‧‧‧Client

I‧‧‧ Invalid packet

V‧‧‧Valid packet

S1‧‧‧Setting procedure

S2‧‧‧ adjustment procedure

S21‧‧‧Abandonment steps

S22‧‧‧ judgment steps

S23‧‧‧Filter step

S24‧‧‧Transfer steps

S3‧‧‧ Reorganization procedure

Figure 1: Schematic diagram of three adjustable modes of H.264/SVC video compression technology.

Figure 2a: Schematic diagram of spatially tunable coding/decoding reference relationship for H.264/SVC video compression technology.

Figure 2b: Schematic diagram of spatially tunable coding/decoding reference relationship for H.264/SVC video compression technology.

Figure 2c: Schematic diagram of the quality-adjustable encoding/decoding reference relationship of H.264/SVC video compression technology.

Figure 3a is a schematic diagram of coding dependencies (1) of a preferred embodiment of the video transmission control method of the present invention.

Figure 3b is a schematic diagram of coding dependencies (2) of the preferred embodiment of the video transmission control method of the present invention.

Figure 4 is a system architecture diagram of a preferred embodiment of the video transmission control method of the present invention.

Figure 5 is a flow chart showing the operation of the preferred embodiment of the video transmission control method of the present invention.

Figure 6a: Schematic diagram of packet transmission control of the gateway of the present invention (1).

Figure 6b: Schematic diagram of packet transmission control of the gateway of the present invention (2).

Figure 6c: Schematic diagram of packet transmission control of the gateway device of the present invention (3) ).

Figure 7 is a diagram showing the test results of a preferred embodiment of the video transmission control method of the present invention.

S1. . . Setting procedure

S2. . . Adjustment procedure

S21. . . Discard step

S22. . . Judgment step

S23. . . Filtering step

S24. . . Transfer step

S3. . . Reorganization procedure

Claims (4)

A video transmission control method includes: a setting program, wherein a server divides a frame of a different stream of data into a plurality of packets, and then sets each packet according to a group priority, and then transmits The packet is sent to a gateway, and the gateway temporarily stores the packet from the server; and an adjustment procedure is determined by the gateway according to the temporary storage capacity of the packet to determine whether to discard the lower priority. The packet is further determined whether each packet belongs to the same group. If the determination is yes, the packets are regarded as valid or invalid according to the coding dependency between the frames. If the determination is no, the transmission is regarded as valid. The packet is encapsulated to a client; wherein the adjustment procedure includes: a discarding step, wherein the gateway determines whether the temporary storage capacity of the packet is higher than a threshold upper limit, and if the determination is yes, discarding the temporarily stored packet If the judgment is negative, the packet from the server is continuously received; in the determining step, it is determined by the gateway whether the temporarily stored packets belong to the same group, and if the determination is yes, then One The filtering operation, if the determination is no, performs a packet transmission operation; in a filtering step, the packet filtering operation is performed by the gateway device, and the frame itself and the reference signal are judged according to the coding dependency between the frames. Whether the packets of the frame have been collected, and if the judgment is yes, the packets of the frame itself are regarded as valid. If the determination is no, the packets of the frame itself are regarded as invalid; In a transmitting step, the packet transmission operation is performed by the gateway, and the packet deemed to be invalid is discarded, and the packet deemed to be valid is transmitted to the client. The video transmission control method according to claim 1, further comprising a recombination program, wherein the client forms a valid packet into the frame, and trims the frame that cannot be decoded according to the coding dependency between the frames. . The video transmission control method of claim 1, wherein the discarding step determines whether the temporary storage capacity is higher than a lower threshold of the gateway, and if the determination is yes, maintaining the current The temporary storage capacity, if the determination is negative, continues to receive the packet from the server, wherein the lower threshold of the gateway is lower than the upper limit of the gateway. The video transmission control method according to claim 1 or 2, wherein the server sets the packet according to a time, a space and a quality adjustable parameter of the streaming data from small to large. Priority is from high to low.