KR20070027780A - Method for changing channel - Google Patents

Abstract

A method for controlling channel change is provided to reduce a channel changing speed using a plurality of video buffers. A method for controlling channel change in a digital broadcasting receiver having at least one tuner and a video buffer includes a step of tuning a channel, storing a signal of the channel in a predetermined region of the video buffer, decoding the signal and displaying an image corresponding to the signal, a step of tuning at least one reserve channel and storing a signal of the reserve channel in a predetermined region of the video buffer, and a step of reading the signal of the reserve channel from the video buffer, decoding the read signal and displaying an image corresponding to the decoded signal when a channel to be changed corresponds to the reserve channel.

Description

How to control channel switching {Method for changing channel}

1 is a flow chart showing the process from the conventional channel switching to the screen output

2 is a block diagram showing an embodiment of a digital broadcast receiver according to the present invention;

3 is a flowchart illustrating a process from channel switching to screen output according to the present invention.

4 is a block diagram showing another embodiment of a digital broadcast receiver according to the present invention;

Explanation of symbols for main parts of the drawings

210: tuner portion 220: demodulation portion

230: demultiplexer 241,242: video decoding unit

250: memory 260: control unit

The present invention relates to a digital broadcast receiver, and more particularly, to a method for fast channel switching of a digital broadcast channel.

In general, there are various cases where channel switching may occur in a receiver. For example, the user may change the channel directly, or the channel may be automatically changed by reserved viewing.

At this time, the analog broadcast channel is switched from the previous channel to the next channel, and there is little delay time until the next channel is normally displayed, whereas the digital broadcast channel has a significant delay time.

This is because, in the case of digital broadcasting, when a channel switching command is input, the video buffer is initialized, and video decoding for the channel to be switched starts only after the decoding condition is satisfied.

That is, when a channel change command is input, the sequence buffer is initialized and the sequence header, which is an access point that starts decoding while storing the video bitstream of the channel to be switched, is found. From the sequence header, decoding starts until the system clock approaches the Decoding Time Stamp (DTS) value. Subsequently, after decoding a certain number of pictures for the channel to be switched, the video screen of the converted channel can be viewed.

Due to the above processing, in the case of digital broadcasting, delay time due to channel switching may occur up to about 2 seconds.

1 shows a process from changing a channel to outputting a screen of a general digital broadcasting.

The digital broadcast receiver for receiving and processing the digital broadcast is largely comprised of a tuner, a demodulator, a demultiplexer, a video buffer, a video buffer controller, a video decoder, and a display processor.

That is, when the digital broadcast signal passes through the tuner and the demodulator, it is input to the demultiplexer in the form of a bitstream. The demultiplexer separates the video, audio, and data streams from the multiplexed bitstream and then outputs the video stream to the video decoding unit through the video buffer.

At this time, the video buffer controller writes an input video stream to the video buffer while updating a write pointer of the video buffer. In this case, an external synchronous DRAM (SDRAM) or the like may be used as the video buffer, and the size of each video standard determines an appropriate value. During viewing of one channel, a write operation at an input rate and a read operation for decoding according to the DTS based on the system clock (STC) are performed and buffer control is performed.

If a channel change command is input (step 101), the tuner and demodulator tune and demodulate the channel to be changed (step 102). The demodulated signal is input to the demultiplexer in the form of a transport stream (TS). The demultiplexer separates the video, audio, and data streams of the program selected by the user from the transport stream input with reference to Program specification information (PSI) (step 103).

Since the TS transmits a plurality of video and audio individual bit streams, it is necessary to select one of a plurality of programs and then to know the packet recognition number (PID) of the transport packet of the individual bit streams required for decoding / reproducing the program. . After that, it is necessary to know parameter information or association information of these individual bit strings. A plurality of side information (PSI) tables are required for this multi-step operation, and these tables are transmitted by a data structure called a section.

The video stream separated by the demultiplexer is output to the video decoding unit through a video buffer.

In this case, when the channel is switched, the video buffer controller initializes the write pointer and the read pointer of the video buffer, and outputs the video stream of the channel to be changed to the video decoder through the video buffer. Accordingly, the video decoding unit ignores the video stream of the previous channel stored in the video buffer and starts decoding on the video stream of the newly input channel. In this case, the decoding does not start immediately, but is performed when the access point is found (step 104), and the difference between the system clock (STC) and the DTS of the corresponding picture is within a predetermined range (Ndiff) (step 105). The access point becomes a sequence header in the case of MPEG-2.

The video signal reconstructed as the original signal by the video decoding unit is displayed on the screen after the format conversion, reordering processing, etc. are performed by the display processing unit (step 106).

However, when changing the channel of the digital broadcasting, the demultiplexer parses the program specification information (PSI) to set the PID of the video, audio, and data stream of the corresponding program (TDdmux), and the video decoder access point of the video buffer. The waiting time (TDvbuff) takes up more than 90% until the system clock (STC) reaches the DTS and Ndiff.

In other words,

TDdmux = PSI packet seek time + time spent setting PID

TDvbuff = Time to find access point + time to wait near DTS.

Therefore, when the viewer directly changes the digital broadcast channel or automatically changes the digital broadcast channel due to the reserved viewing, there is a delay of a certain time before changing to the next channel and viewing the screen of the channel.

This delay is inconvenient for the viewer.

The present invention is to solve the above problems, an object of the present invention to provide a method for reducing the channel switching speed.

Another object of the present invention is to provide a method for reducing a channel switching speed by using a plurality of video buffers.

In order to achieve the above object, a channel switching control method of a digital broadcast receiver having at least one tuner and a video buffer according to the present invention,

(a) tuning one viewing channel, storing it in a corresponding area of the video buffer, and decoding and displaying the same;

(b) tuning and storing at least one spare channel in a corresponding region of the video buffer; And

(c) if the channel to be switched coincides with the spare channel of step (b), the video signal of the spare channel is read from the video buffer, decoded, and then displayed.

The preliminary channel is determined as one of the front channel and the rear channel of the current channel according to the channel change direction.

The preliminary channel is determined as a channel immediately preceding the current channel.

The preliminary channel is determined as a channel having the highest viewing preference.

The reserved channel may be determined as a reserved channel when reserved viewing is performed.

The step (c) includes setting a position N leading from the current write pointer position in the video buffer in which the spare channel to be read is stored as a read pointer, and reading, decoding, and displaying a video signal from the read pointer. Characterized in that made.

The step (c) is to find the I picture of the previous time closest to the current write pointer position in the video buffer in which the reserved channel to be read is set as a read pointer, and to read, decode and display the I picture of the read pointer. Characterized in that comprises a step.

Other objects, features and advantages of the present invention will become apparent from the following detailed description of embodiments taken in conjunction with the accompanying drawings.

Hereinafter, with reference to the accompanying drawings, preferred embodiments of the present invention that can specifically realize the above object will be described. At this time, the configuration and operation of the present invention shown in the drawings and described by it will be described as at least one embodiment, by which the technical spirit of the present invention and its core configuration and operation is not limited.

The present invention allocates the video buffer area larger than the reference area so that more than one program can be processed, and reduces the channel switching speed by using the allocated video buffer. Here, the reference area is a buffer size that can process one program.

That is, while simultaneously storing the video stream of the channel being watched and the video stream of the preliminary channel selected in a predetermined order in the video buffer, the video stream of the channel being watched is read by the video decoding unit to perform decoding. Do not decode the video stream of the spare channel.

If a channel change command is input and the channel to be changed matches the spare channel stored in the video buffer, the read pointer program is read by changing only the read pointer to the position where the spare channel is stored without initializing the video buffer. Decode and display.

The read pointer is set to an address N ahead of the write pointer in the video buffer where the video stream of the spare channel is stored (read pointer = write pointer-N). Here, N is set to a value that can prevent overflow considering the input rate of the video stream.

At this time, if the digital broadcast receiver is a receiver capable of decoding and displaying only one channel program, the size of the video buffer should be extended.

However, a receiver capable of simultaneously processing a plurality of programs as shown in FIG. 2 or a receiver capable of simultaneously processing a plurality of programs (for example, four) as shown in FIG. 4 may already process more than one program. The video buffer is allocated so that it does not need to be allocated separately for the present invention. However, in the case of FIG. 2, the TV screen currently being viewed should be a single screen, and in FIG. 4, at least one video buffer area should be left for the reserved channel.

2 is a conceptual diagram of a digital broadcast receiver capable of simultaneously decoding and displaying a plurality of programs. The tuner 210, the demodulator 220, and the demultiplexer 230 simultaneously tune and demodulate a plurality of channels CH0 and CH1. , And demultiplexing. The video streams of the two channels separated by the demultiplexer 230 are stored in the corresponding video buffer region in the memory 250 through the video buffer controllers V0 and V1 in the video decoding units 241 and 242.

In this case, if the simultaneous picture viewing is selected, the video stream stored in each video buffer is a video stream of a channel selected by the user. The video stream is output to each video decoder under the control of the video buffer controller, decoded, and then displayed in the simultaneous picture form.

However, in a single screen, the video stream stored in one video buffer is the video stream of the channel selected by the user, and the video stream stored in the other video buffer is the video stream of the spare channel for channel switching. In this case, the video stream of the channel selected by the user under the control of each video buffer controller is output to the corresponding video decoder, decoded, and then displayed on a single screen. The video stream of the spare channel is discarded at regular intervals through overwrite and so on unless there is a channel change.

In this case, the video buffer may be used by allocating a partial area in the memory (DDR SDRAM) 250 or may be separately configured externally.

The selection and / or method of preliminary channels to be stored in the video buffer in advance may be set in consideration of a user's habit or viewing situation, or may be automatically set by the system.

For example, there is a method of continuously changing a spare channel, a method of setting a channel immediately before the current channel as a spare channel, and a method of setting a channel having the highest preference as a spare channel. Alternatively, when reserved viewing is performed, the reserved channel may be set as a reserved channel. The method of selecting the spare channel may be variously applied according to the designer, and thus the present invention is not limited to the example provided above.

The first method is suitable for the situation of watching the entire channel in order to select a channel to watch. In this case, the range of channel selection may be set to all channels with a signal, a list of channels registered by the viewer with a signal, or a list of channels registered by the viewer regardless of the signal. Using the channel list as an example, the video buffer controller performs video buffer control on a channel immediately before or after the current channel. The direction setting for the front channel or the back channel of the current channel depends on whether the previous channel change was forward or reverse. For example, if the viewer is performing channel change in the channel up direction, the channel behind the current channel is determined as the spare channel.

The second method is to set the channel before the channel change as a spare channel, which is advantageous in view of alternating two channels. In other words, if you are looking at the other channel first while waiting for the desired program to start on one channel, this is a quick way to switch between the two channels. For example, if 11 and 9 are alternately viewed, channel 11 is set as a spare channel when 11 is displayed, and channel 11 is set as a spare channel when 9 is displayed.

The third method is to set the preferred channel list or the rank of the preferred channel and set the channel with the highest preference as the spare channel besides the channel currently being viewed.

The video streams of the spare channels selected by any of the above methods are stored in the corresponding video buffer together with the video streams of the channel currently being viewed.

In this case, the size of the video buffer for the spare channel may be allocated to the size of the base area, that is, the same size as the video buffer size of the channel for viewing, or larger than the base area.

If at least one I picture of the spare channel is allocated larger than the base size so that it can always be stored in the video buffer, the channel change time can be further shortened. For example, if the video buffer for the spare channel is allocated to have a size twice as large as the base size, the corresponding video buffer controller creates an index for the position of the sequence header in the video buffer for the spare channel. That is, the video buffer control unit manages the access point location such as the sequence header and controls to read from the corresponding location at the start of decoding.

If a channel change command is input and the channel to be changed is identical to the spare channel, the read pointer is set to the I picture position having the smallest α by Equation 1 below. That is, the I picture of the previous time nearest to the current write pointer position in the video buffer for the reserved channel is found and set as the read pointer.

Temporary Address (TmpAddr) = Write Address-Buffer Size / 2-α

Read pointer = temporary address + buffer size, temporary address <0

            = Temporary address, temporary address ≥ 0

When the read pointer is set by Equation 1, the I picture of the read pointer is read and decoded. At this time, only the I and P pictures are decoded until the DTS-STC is within a certain range. If the DTS-STC is within a certain range, the B picture is also decoded.

3 shows a process from channel change to screen output in digital broadcasting according to the present invention.

In the case of FIG. 3, it is assumed that the channel to be changed when the channel change is input while the video stream of the spare channel is being stored in the at least one video buffer coincides with the spare channel (step 301).

Then, a read pointer is set to read an I picture of the previous time closest to the current DTS in the same manner as in Equation 1 above (step 302), and the I picture read from the read pointer is decoded. At this time, the position information of the I picture for searching for a near I picture may be used by making an I picture position list having an index by analyzing only the type information when the video stream is input (step 303). After decoding the I picture, it is an initial processing interval until decoding a picture having a DTS within a predetermined range of the STC. That is, only the I and P pictures are decoded until the difference between the system clock (STC) and the DTS of the corresponding picture is in a certain range (Ndiff) (steps 304 to 306, and 308). Decode (steps 304, 306, and 308).

The picture output may be shown immediately after decoding the I picture or after the initial processing section ends (step 307). In this case, only I and P pictures are decoded in the initial processing section, and all pictures are decoded and output after the initial processing section is finished.

This allows the screen to be visible within one second, even in the worst case, which can reduce the channel change delay value by more than one second.

4 shows an example of a receiver capable of simultaneously tuning, demodulating, and decoding four programs, which is one way to increase the number of spare channels. FIG. 4 shows an example of a structure in which four channels can be simultaneously stored in a video buffer, and video decoding is performed simultaneously on two channels by a plurality of video decoders 461 and 462. To this end, first and second selectors 451 and 452 are provided. Each video buffer for four programs may be used by allocating a partial region in the memory (DDR SDRAM) 470 or may be separately configured externally. Each video buffer is controlled independently through each of the video buffer controllers V0 to V3.

In the case of FIG. 4, up to three spare channels may be set and stored in the video buffer. In this case, the selection of the spare channel may be set in combination with at least one of the above-described methods.

As described above, the present invention stores a preliminary channel video stream using a video buffer other than the video buffer for the channel being watched. Read, decode and display. In this way, since the video buffer does not need to be initialized when changing the channel, the overall channel search time can be shortened by the number of channels / 2 seconds or more.

That is, according to the present invention, channel switching is performed through video buffer switching instead of video buffer initialization when channel switching, so that channel switching can be performed on average 0.5 seconds or more faster than before.

In addition, when the reserved channel is combined with the reserved viewing through the program guide, the reserved channel can be set so that the channel switching can be performed with the minimum delay time when the reserved viewing time is reached.

On the other hand, the terms used in the present invention (terminology) are terms defined in consideration of the functions in the present invention may vary according to the intention or practice of those skilled in the art, the definitions are the overall contents of the present invention It should be based on.

The present invention is not limited to the above-described embodiments, and as can be seen in the appended claims, modifications can be made by those skilled in the art to which the invention pertains, and such modifications are within the scope of the present invention.

In the channel switching control method according to the present invention described above, if at least one channel or more reserved channels are stored in a video buffer in advance, and a channel change command is input, and if the channel to be changed is identical to the reserved channel, the reserved channel without the video buffer initialization process is performed. By reading, decoding, and displaying the channel, you can reduce the channel switching speed. In particular, the present invention can reduce the channel switching speed by reserved viewing by determining at least one reserved channel as a reserved channel when reserved viewing is performed.

Those skilled in the art will appreciate that various changes and modifications can be made without departing from the spirit of the present invention.

Therefore, the technical scope of the present invention should not be limited to the contents described in the embodiments, but should be defined by the claims.

Claims (9)

A channel switching control method of a digital broadcasting receiver having at least one tuner and a video buffer, (a) tuning one viewing channel, storing it in a corresponding area of the video buffer, and decoding and displaying the same; (b) tuning and storing at least one spare channel in a corresponding region of the video buffer; And and (c) if the channel to be switched coincides with the spare channel of step (b), reading and decoding the video signal of the spare channel from the video buffer and displaying the same. The method of claim 1, wherein the reserve channel is The channel switching control method according to claim 1, characterized in that it is determined by any one of the front channel or the rear channel of the current channel according to the channel change direction. The method of claim 1, wherein the reserve channel is The channel switching control method characterized in that it is determined to be the immediately preceding channel of the current channel. The method of claim 1, wherein the reserve channel is And a channel having the highest viewing preference. The method of claim 1, wherein the reserve channel is The channel switching control method according to claim 1, wherein the reserved channel is determined as a reserved channel. The method of claim 1, wherein step (c) Setting the read pointer to a position N leading from the current write pointer position in the video buffer in which the spare channel to be read is stored; And reading and decoding the video signal from the read pointer and displaying the video signal. The method of claim 6, The N is set to a value that can prevent the overflow of the video signal of the spare channel stored in the video buffer. The method of claim 1, wherein step (c) Finding the I picture of the previous time closest to the current write pointer position in the video buffer where the spare channel to be read is stored and setting it as a read pointer; And reading, decoding, and displaying the I picture of the read pointer. 9. The method of claim 8, wherein said decoding and displaying step Decoding only the I and P pictures until the difference between the system clock (STC) and the decoding time stamp (DTS) of the corresponding picture is within a certain range, and if it is within the predetermined range, all the pictures are decoded and displayed. Way.

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