KR101336820B1 - Apparatus and method for decoding specialized multi-channel trick mode - Google Patents

Abstract

The decoding apparatus selects frames sequentially positioned in the bitstream in reverse order according to an input for requesting reverse playback of the user, selects the target frames, and outputs the encoder and the image generating the encoded images of the target frames. If the target frame is a P frame, the encoder includes an output unit to generate a reference image by encoding the I frame closest to the target frame among the I frames located before the target frame, and with reference to the reference image A P frame is encoded.

Description

Decoding apparatus and method specialized in multi-channel trick mode {APPARATUS AND METHOD FOR DECODING SPECIALIZED MULTI-CHANNEL TRICK MODE}

The present invention relates to a decoding technique, and more particularly, to a decoding apparatus and method for supporting double speed playback and reverse playback.

Codecs based on standards such as H.264 / AVC are mainly used for video compression in surveillance systems. The DVR (Digital Video Recorder) is a device that performs recording and playback for surveillance purposes. In recent years, a surveillance system has been constructed to use a plurality of surveillance cameras, and as the number of cameras increases, the memory capacity of the decoding apparatus increases significantly.

An object of the present invention is to provide a decoding apparatus and method for supporting double speed playback.

An object of the present invention is to provide a decoding apparatus and method for supporting reverse playback.

According to an aspect of the present invention, in accordance with an input for requesting the reverse playback of the user, an encoder for sequentially selecting the frames located in the bitstream in reverse order to select the target frame and to generate an image encoding the target frame; And an output unit configured to output the image, wherein when the target frame is a P frame, the encoder generates a reference image by encoding an I frame closest to the target frame among the I frames located before the target frame, There is provided a decoding apparatus characterized by encoding the P frame with reference to a reference image.

And a storage unit having a first reference buffer and a second reference buffer for storing the reference image for each channel, wherein the encoder stores the reference image in the first reference buffer or the second reference buffer, and A frame may be decoded by referring to a reference image stored in the first reference buffer or the second reference buffer.

The encoder may store the reference image in a buffer that stores a reference image having a later stored time point among the first reference buffer and the second reference buffer.

The storage unit may further include a first decoding buffer and a second decoding buffer, wherein the decoding unit stores the target frame in the first decoding buffer, and stores the frame to be decoded immediately after decoding the target frame in the second decoding buffer. Can be stored.

According to another aspect of the present invention, a frame corresponding to a skipped position according to a magnification of double speed playback requested by a user among frames sequentially positioned in a bitstream is selected as a target frame, and encoding is performed to generate an image obtained by encoding the target frame. part; And an output unit configured to output the image, wherein when the target frame is a P frame, a reference image is generated by encoding an I frame closest to the target frame among I frames positioned before the target frame, and generating the reference image. There is provided a decoding apparatus characterized by encoding the P frame with reference.

According to another aspect of the present invention, in a decoding apparatus having a first reference buffer and a second reference buffer for each channel in decoding a bitstream, the bitstream is sequentially sequenced in accordance with an input for requesting reverse playback of a user. Selecting a frame located in reverse order to select the target frame; If the target frame is a P frame, generating a reference image by encoding an I frame closest to the target frame among the I frames located before the target frame; Generating an output image by encoding the P frame with reference to the reference image; A decoding method including outputting the output image is provided.

The decoding method may further include storing the reference image in the first reference buffer or the second reference buffer, and generating the output image may include storing the reference image in the first reference buffer or the second reference buffer. The method may include generating an output image by encoding the P frame with reference to a reference image.

The storing of the reference picture may include storing the reference picture in a buffer for storing a reference picture having an older stored time point among the first reference buffer and the second reference buffer.

According to still another aspect of the present invention, in a method of decoding a bitstream by a decoding apparatus, a frame corresponding to a position skipped according to a magnification of a double speed reproduction requested by a user among frames sequentially positioned in the bitstream is a target frame. Selecting a step; If the target frame is a P frame, generating a reference image by encoding an I frame closest to the target frame among the I frames located before the target frame; Generating an output image by encoding the P frame with reference to the reference image; A decoding method including outputting the output image is provided.

According to the embodiment of the present invention, the capacity of the memory required for reverse playback can be reduced.

According to the embodiment of the present invention, it is possible to reduce the computational complexity due to double speed reproduction.

According to an embodiment of the present invention, it is possible to provide a double speed reproduction function for showing an image of natural movement.

1 is a block diagram schematically illustrating a decoding apparatus.
2 is a diagram illustrating a bitstream received by a decoding apparatus.
3 is a diagram illustrating in detail a buffer provided in a storage unit of a decoding apparatus.
4 is a diagram illustrating a sequence of frames decoded by the decoding apparatus for reverse reproduction in the bitstream illustrated in FIG. 2.
5 is a diagram illustrating an order in which frames of a bitstream are decoded when the decoding apparatus performs double speed reproduction.
6 is a flowchart illustrating a process of decoding a bitstream by a decoding apparatus.

While the present invention has been described in connection with certain exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and similarities. It should be understood, however, that the invention is not intended to be limited to the particular embodiments, but includes all modifications, equivalents, and alternatives falling within the spirit and scope of the invention.

Further, in this specification, when an element is referred to as " transmitting " a signal to another element, the element can be directly connected to the other element to transmit a signal, It should be understood that the signal may be transmitted by mediating another component in the middle.

FIG. 1 is a block diagram briefly illustrating a decoding apparatus, FIG. 2 is a diagram illustrating a bitstream received by a decoding apparatus, and FIG. 3 is a diagram illustrating in detail a buffer provided in a storage unit of the decoding apparatus.

Referring to FIG. 1, the decoding apparatus includes a receiver 110, a decoder 120, a storage 130, and an output 140.

The receiver 110 receives the bitstream from the outside. In this case, the receiver 110 may be connected to the encoding device or the storage device storing the bitstream through the communication network, and may receive the bitstream from the encoding device or the storage device through the communication network. In this case, the bitstream received by the receiver 110 may be a bitstream obtained by encoding a video in a keyframe mode. The key frame mode is a mode in which a bitstream including an I frame and a P frame is generated, but the P frame is encoded by referring to only the I frame. 2, each frame of the bitstream encoded in the key frame mode in the order displayed in normal playback (1x forward playback) is illustrated. I frame I1 is a frame that is first decoded and output in the bitstream during normal playback, and I frame I3 is the last frame output. P frames P1 and P2 are frames encoded with reference to I1. In addition, I frame I2 is a frame immediately after P1 during normal playback, and P3 and P4 are frames encoded with reference to I2. In addition, I1, P1, and P2 are frames obtained by encoding an image corresponding to a first channel, and I2, P3, and P4 are frames encoded by a video corresponding to a second channel. In this case, the image corresponding to the first channel may be an image generated by the first camera among the plurality of cameras, and the image corresponding to the second channel may be an image generated by the second camera among the plurality of cameras.

The decoder 120 generates an image by decoding a frame included in the bitstream received by the receiver 110. In this case, the decoder 120 may decode the bitstream to be reproduced by any one of normal reproduction, double speed reproduction, and reverse reproduction. The decoder 120 may store data necessary for the decoding process by using the buffer provided in the storage 130. Hereinafter, the decoder 120 performing reverse playback and double speed playback will be described in detail with reference to FIGS. 3 and 4. The decoder 120 transmits the image to the output unit 140.

The storage unit 130 includes a decoding buffer and a reference buffer to store data that needs to be stored in the decoding process of the decoder 120. Referring to FIG. 3, the storage unit 130 may include a first decoding buffer 310, a second decoding buffer 315, a plurality of first reference buffers 320, 330, and 340, and a plurality of second reference buffers 325. , 335, 345). The first decoding buffer 310 and the second decoding buffer 315 store the I frame or P frame extracted by the decoder 120 from the bitstream. For example, the decoder 120 extracts a frame to be decoded from the bitstream, stores the frame to be decoded in the first decoding buffer 310, decodes the frame stored in the first decoding buffer 310, and then decodes the frame. The frame may be stored in the second decoding buffer 320. In this case, the first decoding buffer 310 and the second decoding buffer 315 stores only I frames, and separate first decoding buffers (not shown) and second decoding buffers (not shown) further include a storage unit ( 130 may be changed to store only the P frame. The first reference buffers 320, 330, and 340 and the plurality of second reference buffers 325, 335, and 345 may be matched for each channel, and may store images decoded I frames of the corresponding channels. For example, the first reference buffer 320 and the second reference buffer 325 may store an image obtained by decoding an I frame corresponding to the first channel. In this case, the first decoding buffer 310, the second decoding buffer 315, the plurality of first reference buffers 320, 330, and 340, and the plurality of second reference buffers 325, 335, and 345 are one. You can store data for one frame per buffer. 4 and 5, the process of the decoder 120 storing data for a frame in the storage 130 will be described in detail.

The output unit 140 receives an image from the decoder 120 and outputs the corresponding image. In this case, the output unit 140 may include a display module (eg, a monitor) capable of displaying an image and output the image. In addition, the output unit 140 may transmit an image to an external display module through a communication network.

4 is a diagram illustrating a sequence of frames decoded by the decoding apparatus for reverse reproduction in the bitstream illustrated in FIG. 2. Hereinafter, the decoding apparatus 120 extracts a frame from the bitstream and stores the frame in the first decoding buffer 310 or the second decoding buffer 315 and decodes the stored frame. For the sake of brevity and clarity, the process of storing a frame in the first decoding buffer 310 or the second decoding buffer 315 and the process of decoding the frame will be described as decoding.

Referring to FIG. 4, the decoder 120 may receive an input for requesting reverse playback from a user. The decoder 120 decodes the bitstream in reverse frame units in response to a request for reverse playback. That is, the decoder 120 performs decoding in the order of frames I3 to I1 frames located at the end of the bitstream.

For example, the decoder 120 decodes the frame I3 located at the end of the bitstream (the last frame of the bitstream) and transmits the same to the output unit 140. At this time, the decoder 120 may decode I3 without reference to another frame since I3 is an I frame. The decoder 120 stores the image generated by decoding I3 in the first reference buffer 330. The decoder 120 then attempts to decode P4, which is the frame immediately before I3. At this time, the decoder 120 confirms that the I2 frame used as the reference frame for encoding P4 is not decoded because P4 is a P frame. The decoder 120 preferentially decodes the I2 frame in order to decode P4. At this time, the decoder 120 stores the image obtained by decoding the I2 frame in the second reference buffer 335. Thereafter, the decoder 120 decodes P4 by referring to the image stored in the second reference buffer 335 and transmits the decoded P4 to the output unit 140. The decoder 120 decodes P3, which is the frame immediately before P4. In this case, since P3 is a frame encoded with reference to I2 as in P4 and the image obtained by decoding I2 is stored in the second reference buffer 335, the decoder 120 may determine P3 without encoding an additional I frame. Decode and transmit to the output unit 140. The decoder 120 then attempts to decode P2. At this time, the decoder 120 confirms that I1 which is the reference frame of P2 is not decoded and decodes I1. The decoder 120 stores the image obtained by decoding I1 in the first reference buffer 320. The decoder 120 decodes P2 by referring to the image stored in the first reference buffer 320. Subsequently, the decoder 120 extracts I2, which is the frame immediately before P2, from the second reference buffer 335 and transmits the same to the output unit 140. The decoder 120 decodes P1 with reference to the first reference buffer 320 and transmits the P1 to the output unit 140. The decoder 120 transmits the image stored in the first reference buffer 320 to the output unit 140.

As described above, the decoding apparatus performs a process of selecting and decoding only frames to be output from the bitstream, not a method of decoding the plurality of frames and outputting them in reverse order. Therefore, the decoding apparatus has a small size of the buffer required for reverse reproduction, so that the memory required for configuring the decoding apparatus can be reduced.

FIG. 5 is a diagram illustrating an order in which frames of a bitstream are decoded when the decoding apparatus performs double speed reproduction. The bitstream illustrated in FIG. 5 is assumed to be a bitstream including only frames for one channel.

Referring to FIG. 5, the decoder 120 decodes I1, which is the first frame of the bitstream, and transmits the same to the outputter 140. At this time, the decoder 120 stores the image obtained by decoding I1 in the first reference buffer 320. The decoder 120 decodes a frame in which a frame is skipped from a previously decoded frame according to the magnification of the double speed reproduction. For example, the decoder 120 skips decoding of P1, which is the next frame of I1, and performs decoding of P2 as the magnification of the 2x reproduction is doubled. The decoder 120 decodes P2 with reference to the image stored in the first reference buffer 320 and transmits the P2 to the output unit 140. The decoder 120 skips I2, the next frame of P2, and attempts to decode P3. At this time, the decoder 120 confirms that I2 necessary for the decoding of P3 is not decoded and decodes I2. The decoder 120 stores the image obtained by decoding I2 in the second reference buffer 325. The decoder 120 decodes P3 by referring to the image stored in the second reference buffer 325 and transmits the P3 to the output unit 140. The decoder 120 skips P4, which is the next frame of P3, and decodes I3 to transmit it to the output unit 140.

As described above with reference to FIG. 5, the decoding apparatus may reduce the load generated during the decoding process by omitting decoding of a frame that is not output in double speed playback. In addition, the conventional decoding method for double speed reproduction is a method of outputting an I frame closest to the corresponding P frame when the frame to be output according to the magnification is a P frame. Since the video output by the conventional decoding method does not output the P frame itself, the motion of the output video is not constant, and thus the video that is double-speed reproduction is unnatural. The decoding apparatus according to an embodiment of the present invention may output the P frame itself to be output according to the magnification.

In this case, the above-described matter with reference to FIG. 5 has been described in the case of double-speed playback, but when the magnification of the double-speed playback is different, the decoding apparatus may determine that the frame skipped from the previously decoded frame according to the magnification of the double-speed playback. It will be apparent to those skilled in the art that decoding can be performed.

6 is a flowchart illustrating a process of decoding a bitstream by a decoding apparatus. The decoding apparatus described below is assumed to decode the bitstream in response to a reverse playback request of the user.

Referring to FIG. 6, in step 610, the decoding apparatus selects any one of a plurality of frames included in the bitstream as a target frame in a decoding order for reverse playback. In this case, the target frame refers to a frame to be decoded by the decoding apparatus. That is, the decoding apparatus selects the target frame in the order from the frame located at the last end to the frame located at the foremost end of the bitstream.

In operation 620, the decoding apparatus determines whether the target frame is an I frame.

If the target frame is not an I frame in step 620, the decoding apparatus determines whether the I frame referenced by the target frame is decoded in step 630.

If the I frame referenced by the target frame is not decoded in step 630, in step 640, the decoding apparatus selects the I frame referred to by the P frame that is the current target frame as the target frame.

In operation 650, the decoding apparatus decodes the target frame to generate an image, and stores the generated image in a reference buffer. At this time, the process of storing the image in the buffer has been described above with reference to FIG.

In operation 660, the decoding apparatus selects the P frame, which was the target frame, in operation 640 as the target frame, and performs the process from operation 620 again.

If the I frame referenced by the target frame is decoded in step 630, the decoding apparatus decodes the target frame in step 670 to generate an image and output the image. In this case, when the target frame is an I frame that is already decoded in operation 650, the decoding apparatus may extract and output an image corresponding to the I frame from the reference buffer without performing a separate decoding process.

If the target frame is an I frame in step 620, the decoding apparatus performs step 670 described above.

In operation 680, the decoding apparatus determines whether an undecoded frame exists in the bitstream.

If there is no frame decoded in step 680, the process from step 610 is repeated.

If there is no frame that has not been decoded in step 680, the decoding apparatus ends the decoding process.

So far, the process of decoding the bitstream by the decoding apparatus when the user requests reverse playback has been described with reference to FIG. 6. Hereinafter, a process of decoding the bitstream by the decoding apparatus when the double speed reproduction is requested will be described with reference to FIG. 6. At this time, since the processes of steps 620 to 680 are the same as the decoding process according to the reverse playback described above, description thereof will be omitted.

In operation 610, the decoding apparatus selects one of the frames included in the bitstream as the target frame according to double speed reproduction. That is, the decoding apparatus selects, as a target frame, a frame positioned after the number of frames according to the magnification of the double speed reproduction from the frame corresponding to the recently output image among the frames included in the bitstream.

The present invention has been described above with reference to the embodiments thereof. Many embodiments other than the above-described embodiments are within the scope of the claims of the present invention. It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. The disclosed embodiments should, therefore, be considered in an illustrative rather than a restrictive sense. The scope of the present invention is defined by the appended claims rather than by the foregoing description, and all differences within the scope of equivalents thereof should be construed as being included in the present invention.

Claims (9)

A decoder configured to sequentially select frames sequentially positioned in the bitstream as a target frame according to an input for requesting reverse playback of a user, select a target frame, and decode the target frame to generate an image;
An output unit for outputting the image; And
The apparatus may further include a storage including a first reference buffer and a second reference buffer for storing a reference image for each channel.
Including,
When the target frame is a P frame, the decoder generates the reference image by encoding an I frame closest to the target frame among the I frames located before the target frame based on a frame alignment direction in the bitstream. The P frame is decoded with reference to a reference image,
The decoding unit stores the reference picture in the first reference buffer when the reference picture corresponds to the first channel, and stores the reference picture in the second reference buffer when the reference picture corresponds to the second channel. And a reference frame stored in the reference buffer and decoded with reference to the reference image stored in the first reference buffer or the second reference buffer.
delete delete The method according to claim 1,
The storage unit further includes a first decoding buffer and a second decoding buffer,
And the decoding unit stores the target frame in the first decoding buffer and stores the frame to be decoded immediately after decoding the target frame in the second decoding buffer.
A decoder which selects a frame corresponding to a skipped position according to a magnification of double speed playback requested by a user among frames sequentially positioned in the bitstream as a target frame, and decodes the target frame to generate an image;
An output unit for outputting the image; And
The apparatus may further include a storage including a first reference buffer and a second reference buffer for storing a reference image for each channel.
Including,
When the target frame is a P frame, the decoder generates the reference image by decoding an I frame closest to the target frame among the I frames located before the target frame based on a frame alignment direction in the bitstream. The P frame is decoded with reference to a reference image,
The decoding unit stores the reference picture in the first reference buffer when the reference picture corresponds to the first channel, and stores the reference picture in the second reference buffer when the reference picture corresponds to the second channel. And a reference frame stored in the reference buffer and decoded with reference to the reference image stored in the first reference buffer or the second reference buffer.
A decoding apparatus having a first reference buffer and a second reference buffer for each channel, the method for decoding a bitstream,
(a) selecting, in reverse order, frames sequentially positioned in the bitstream according to an input for requesting reverse playback of the user, and selecting the target frames;
(b) when the target frame is a P frame, generating a reference image by decoding an I frame closest to the target frame among I frames positioned before the target frame based on a frame alignment direction in the bitstream;
(c) if the reference picture is a picture corresponding to a first channel, storing the reference picture in the first reference buffer;
(d) if the reference picture is a picture corresponding to a second channel, storing the reference picture in the second reference buffer; And
generating an output image by decoding the P frame with reference to the reference image;
(f) outputting the output image
Including,
The step (e)
And decoding the P frame with reference to the reference image stored in the first reference buffer or the second reference buffer to generate an output image.
delete delete A decoding apparatus having a first reference buffer and a second reference buffer for each channel, the method for decoding a bitstream,
(a) selecting a frame corresponding to a skipped position according to a magnification of double speed reproduction requested by a user among frames sequentially positioned in the bitstream as a target frame;
(b) when the target frame is a P frame, generating a reference image by decoding an I frame closest to the target frame among I frames positioned before the target frame based on a frame alignment direction in the bitstream;
(c) if the reference picture is a picture corresponding to a first channel, storing the reference picture in the first reference buffer;
(d) if the reference picture is a picture corresponding to a second channel, storing the reference picture in the second reference buffer; And
generating an output image by decoding the P frame with reference to the reference image;
Outputting the output image
Including,
The step (e)
And decoding the P frame with reference to the reference image stored in the first reference buffer or the second reference buffer to generate an output image.

Images