JPH07143477A - Motion picture data decoding system - Google Patents

Abstract

PURPOSE:To attain smooth video display sufficiently compatible with a frame rate of a video signal by improving an average read rate of coded motion picture data from a picture file device. CONSTITUTION:A decoding circuit 5 is provided with a header detection section 511 separating read motion picture data MR into a time stamp T and a picture data part F and outputting them respectively, a register 52 storing a storage value TR of the time stamp T, a timer 53 applying time data TT and a comparator 54 detecting the coincidence between the stored data TR and the time data TT to control the application of a read control signal CR. The read of a motion picture data M from a decoded buffer 2 is started by a start signal S and the read is interrupted by the detection of the time stamp T and the reading is restarted by the detection of the coincidence to decode the picture data part F.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a moving picture data decoding system, and more particularly to a moving picture data decoding system for decoding coded moving picture data from a digital communication line or a moving picture file device.

[0002]

2. Description of the Related Art In recent years, with the progress of high-efficiency coding technology for image signals, it has become possible to greatly compress moving image data, and a moving image is produced by an image file device such as an ordinary digital communication line or a CDROM for storing digital data. It has become possible to handle image data economically.

Each of the moving image data encoded by the high-efficiency encoding technique is composed of compressed data of a plurality of frames of images, and the data of each frame includes an image data section which is the compressed data of the image. A time stamp indicating each decoding start time is added before.

Between the encoding device and the decoding system,
The communication line and the image filing device having a constant data rate (rate) are interposed, while the moving image data has a data rate depending on the degree of data compression in the image data part of each frame, as described later. (Amount) is different.
Therefore, the decoding system absorbs the fluctuation of the data rate by arranging a buffer memory on each of the transmitting side and the receiving side for the speed adjustment and transmitting at a constant data rate between them. Further, the decoding start timings thereof are not constant, so that it is necessary to set the decoding start timing for each frame. Further, when the data rate of the encoding process is higher than the data rate of the decoding process, the image data of the next frame is supplied although the image data portion of the previous frame in the reception buffer remains. It is necessary to control so as to prevent the overflow of the reception buffer due to the above situation.

As an example of a conventional decoding system of this type, Japanese Patent Laid-Open No. 58-139568 describes a method of decoding coded data (not necessarily moving image data) via a communication line. That is, the transmission side is provided with a transmission buffer memory and its control circuit, and the reception side is provided with a reception buffer memory, respectively, while detecting the synchronization signal of the decoding target code data, and calculating the decoding start time of the code data from the detection timing, From the calculated decoding start time, the memory state of the reception buffer memory is monitored, and when it is likely to overflow, the transmission of the code data from the transmission buffer memory is delayed.

Further, a conventional general moving picture data decoding system of this kind for decoding the moving picture data read out from the image filing apparatus is a moving picture data reading operation from the image filing apparatus and an output to a display apparatus. A timing control section for controlling and a decoder for decoding the image data section are provided, and a decoding start operation of the decoder is performed by the timing control section for reading the moving picture data and for decoding the moving picture data. It is controlled by the input to the vessel. In this case, the image filing device corresponds to the encoding device and the communication line.

Referring to FIG. 5, the conventional moving image data decoding system of this type shown in this figure includes an image file device 1 using a CDROM as a medium for storing moving image data, and an image file device 1 The read image data portion F of the moving image data M is output and the output buffer 4
, A decoding buffer 2 for temporarily storing the image data part F supplied from the timing control part 7, and a decoder for decoding and receiving the supply of the read image data part FR from the decoding buffer 2. 3 and an output buffer 4 that temporarily holds the decoded data D until it is output to a display device (not shown).

Referring to FIG. 4 showing the structure of the moving image data M, the moving image data M indicates the head of each data and a 32-bit header portion H for synchronizing the data.
And a time stamp T indicating a decoding start time of a 90 KHz clock pulse count value as a 33-bit digital value, and an image data portion F which is compressed data of an image for one frame. The data rate of the image data portion F varies in the range of about 64 Kbit / S to about 1.5 Mbit / S depending on the compression degree of the data, and thus the length of the data also varies. In the case of 30 frames / S, which is the same as a general television signal, the data length per frame is 2.13K bits to 50K.
Become a bit.

CDRO which is a medium of the image filing device 1
M has a capacity of 450 Mbytes after the format in which sector information is added and the address information and the like are added, the seek time of the image file apparatus 1 is several hundreds mS on average, and the maximum read rate is 150 Kbytes / S.

The decoding system is started up by starting up the timing control section 7 by a starting signal S supplied from the outside. The timing controller 7 receives the moving image data M from the image filing device 1 in response to the read control signal CR.
Is read out, the time stamp T of the read moving image data M is extracted, the read control signal CR is generated, and the remaining image data portion F is output. This image data section F is
It is stored in the sequential decoding buffer 2. The decoding operation of the decoder 3 is performed by the read image data section F supplied from the decoding buffer 2.
It is activated by inputting R. After this activation, the read control signal CR is supplied to the image file device 1 in accordance with the time stamp T extracted by the timing control unit 7, so that the moving image data M of the frame is sequentially read, and the read image data unit via the decoding buffer is read. FR to serial decoder 3
To perform decoding. The decoded data D is sequentially accumulated in the output buffer 4. The timing control unit 7
The output buffer 4 is controlled by the output control signal CB that controls the output of the decoded data, and the output data DO is output to the display device.

As described above, the start of the decoding operation of the decoder 3 is controlled by the input data dependent method, that is, by the input of the read image data portion FR to the decoder 3. Therefore, every time the decoding of the moving image data M for one frame is completed, the reading of the moving image data M from the image filing apparatus 1 is temporarily stopped and the moving image of the next frame is displayed at the time indicated by the time stamp T of the next frame. It is necessary to restart the reading of the image data M. For this restart, a setup time including at least the seek time is required, and the average read rate of the moving image data M is reduced.

Further, when the setup time is longer than the time from the decoding end time of the previous frame to the decoding start time of the next frame of two consecutive frames at a certain frame rate, that is, a frame interval,
By the time the decoding starts, the moving image data cannot be input in time, and it becomes impossible to output the decoded data according to the frame rate.

For example, when the frame rate is 30 frames / S as described above, the frame interval is 33.
mS. On the other hand, the seek time of the image filing apparatus 1 is several hundreds mS on average, and the maximum read rate is 150 Kbytes / S (1200 Kbits / S). Therefore, in the conventional moving image data decoding system, the moving image data M The average read rate is several hundred mS, and it is difficult to decode at the desired frame rate.

[0014]

In the above-mentioned conventional moving picture data decoding system, the decoding operation of the decoder is started by an input data dependent method, that is, the above-mentioned decoder of the moving picture data read from the image filing apparatus. When the setup time for restarting after moving out of moving image data of a certain frame is long as in the above image filing apparatus, decoding start of moving image data of the next frame is started. There is a drawback that the delay and thus the frame rate of the image to be decoded is reduced.

[0015]

A moving picture data decoding system of the present invention encodes a video signal composed of a plurality of frames, and a header portion indicating the beginning of the data of each frame of the plurality of frames and the above data. Moving image data supply means for supplying moving image data including a timing data section indicating a decoding start time and an image data section of the data;
Decoding buffer memory means for temporarily holding the supplied moving image data, decoding means for decoding the read moving image data read from the decoding buffer memory means into video signal data corresponding to the display video signal, and In a moving picture data decoding system, which comprises an output buffer memory means for temporarily holding video signal data, and which receives the supply of the moving picture data from the moving picture data supply means and decodes it into a display video signal, the decoding means While separating the read moving image data into the header portion, the timing data portion, and the image data portion, and supplying the read control signal of the read moving image data to the decoding buffer memory means by detecting the timing data portion. A header detection section for outputting the image data section and the timing data section; A decoder that decodes the image data portion into the video signal data, a register that holds the timing data portion, a timer that supplies time data based on the count value of clock pulses of a predetermined frequency, and a register of the register. Comparing means for detecting a match between the stored value and the time data and controlling the supply of the read control signal,
The reading of the read moving image data from the decoding buffer memory means is started by an activation signal, the reading is interrupted by the detection of the timing data portion, the reading is restarted by the detection of the coincidence, and the image data portion is read by the image data portion. It is characterized in that it is supplied to a decoder to perform decoding.

[0016]

Embodiments of the present invention will now be described with reference to the drawings. Referring to FIG. 1 which is a block diagram showing an embodiment of the present invention, a moving image data decoding system according to this embodiment has an image file device 1, a decoding buffer 2 and an output similar to those described in the above-mentioned prior art. In addition to the buffer 4, a decoding circuit 5 is provided instead of the conventional decoder 3 for receiving the start signal S and the read moving image data MR from the decoding buffer 2 for decoding.

FIG. 2 is a block diagram showing the configuration of the decoding circuit 5.
Referring to FIG.
And a 33-bit register 52 for storing time stamp data, and a 33-bit timer 53 for displaying the current time as a count value of a built-in 90 KHz clock pulse CK.
And a comparator 54 that detects a match between the stored value TR of the register 52 and the timer value TT of the timer 53 and outputs a restart signal RS that restarts the decoding block. The decoding block 51 extracts the header part H and the time stamp T from the read moving image data MR supplied from the decoding buffer 2, outputs the time stamp T and the image data part F, and responds to the activation signal S with the image data. A header detection unit 511 that outputs the read signal CR, a decoder 512 that is similar to the conventional decoder 3 that decodes the image data unit F, and an OR signal of the logical sum of the activation signal S and the reactivation signal RS. An OR circuit 513 that supplies OSR to the detection unit 511 is provided.

The operation of the present embodiment will be described with reference to FIGS. 1 and 2 and FIG. 3 which is a time chart of the present embodiment. First, the activation signal S is supplied to the image file device 1 and the decoding circuit 5. It In response to the supply of the activation signal S, the image filing device 1 sequentially supplies and stores the moving image data M in the decoding buffer 2. Next, the header detection unit 511 of the decoding circuit 5 supplies the image data read signal CR to the decoding buffer 2 in response to the input activation signal S, and the signal CR
In response to the supply of the read moving image data MR read in response to, and the header portion H at the head portion and the time stamp T are extracted, the above reading is temporarily stopped. On the other hand, the extracted time stamp T is stored in the register 52. As described in the above-mentioned related art, the time stamp T is a 33-bit digital value indicating the count value of the 90 KHz clock pulse CK, which corresponds to 26 hours. The register 52 stores the 33-bit digital value as the stored value T
Store as R. On the other hand, the timer 53 is a 33-bit counter that counts the clock pulse CK, and outputs the current time, which is the count value, as the timer value TT.
The comparator 54 compares the stored value TR with the timer value TT, and outputs a restart signal RS to the header detection unit 511 if they match. The header detection unit 511 supplies the image data read signal CR to the decoding buffer 2 in response to the supply of the restart signal RS, and the decoding buffer 2 reads the read moving image data MR which has been interrupted in response to the signal CR. Is restarted and supplied to the header detection unit 511. Since the read moving image data MR whose reading has been restarted is the image data portion F which is the remaining portion from which the header portion and the time stamp T are extracted as described above, the header detection portion 511 is directly input to the decoder 512. Supply. The decoder 512 decodes the supplied image data portion F and sequentially supplies the decoded data D to the output buffer 4. Further, the output buffer 4 is controlled by the output control signal CB to output the output data DO to the display device. When the decoding of the image data part F for one frame is completed, the header detection part 511 reads the moving image data M of the next frame from the decoding buffer 2, extracts the header part H and the time stamp T of this frame, and registers 52. When set to, the reading of the read moving image data MR from the decoding buffer 2 is interrupted again.

On the other hand, as described above, execution / reading of the read moving image data MR from the decoding buffer by the decoding circuit 5 is performed.
Even during the interruption, the reading of the moving image data M from the image file device 1 to the decoding buffer 2 is continuously performed without stopping the activation. Therefore, no setup time such as seek time associated with start-up after stop is required, and the average read rate of the moving image data M from the image file apparatus 1 is 150 which is the maximum read rate corresponding to the continuous read rate.
It can easily be held at K bytes / S, ie 1200 Kbits / S. This is about 64 Kbit / S of the image data F
To a value of about 1.5 Mbit / S, the value is sufficient.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and various modifications can be made. For example, it is also applicable that the external CPU can arbitrarily set the decoding start time by configuring the time stamp storage register so that it can be accessed from the outside without departing from the gist of the present invention. Of course.

[0021]

As described above, in the moving picture data decoding system of the present invention, the decoding means separates the moving picture data into the header portion, the timing data portion and the image data portion, and the above-mentioned image data portion and A header detection unit that outputs the timing data unit, a register that holds the timing data unit, a timer that supplies time data, a match between the stored value of the register and the time data, and a read control signal is supplied. And reading the moving image data from the decoding buffer by a start signal, interrupting the reading by detecting the timing data section, and restarting the reading by detecting the coincidence. By decoding the image data part, the reading of moving image data from the image data file device can be performed continuously without starting and stopping. Since it is possible to improve the average read rate of the moving image signal to the maximum read rate from the image data file device, there is an effect that a smooth image display sufficiently corresponding to the frame rate of the image signal can be performed. .

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a moving image data decoding system of the present invention.

FIG. 2 is a block diagram showing a configuration of a decoding circuit in FIG. .

FIG. 3 is a time chart of the operation of this embodiment.

FIG. 4 is a diagram showing a structure of moving image data.

FIG. 5 is a block diagram showing an example of a conventional moving image data decoding system.

[Explanation of symbols]

 1 Image File Device 2 Decoding Buffer 3,512 Decoder 4 Output Buffer 5 Decoding Circuit 7 Timing Control Unit 51 Decoding Block 52 Register 53 Timer 54 Comparator 511 Header Detection Unit 513 OR Circuit

Claims (2)

[Claims] 1. A header portion indicating a head of data of each frame of the plurality of frames, a timing data portion indicating a decoding start time of the data, and image data of the data. Moving image data supplying means for supplying moving image data, a decoding buffer memory means for temporarily holding the supplied moving image data, and read moving image data read from the decoding buffer memory means for display. Decoding means for decoding the video signal data corresponding to the video signal, and an output buffer memory means for temporarily holding the video signal data,
In a moving picture data decoding system for receiving the moving picture data supplied from the moving picture data supply means and decoding the moving picture data into a display video signal, the decoding means includes the header part and the timing data from the read moving picture data. Section and the image data section are separated and a header detection for supplying a read control signal of the read moving image data to the decoding buffer memory means by detecting the timing data section and outputting the image data section and the timing data section is detected. Unit, a decoder that decodes the image data unit into the video signal data, a register that holds the timing data unit, a timer that supplies time data based on the count value of clock pulses of a predetermined frequency, The read control signal is detected when a match between the value stored in the register and the time data is detected. Comparing means for controlling supply, starting reading of the read moving image data from the decoding buffer memory means by a start signal, interrupting the reading by detection of the timing data portion, and detecting the coincidence by the detection of the coincidence. A moving image data decoding system characterized in that reading is restarted and the image data section is supplied to the decoder for decoding. 2. The moving image data decoding apparatus according to claim 1, wherein said moving image data supplying means is an image data file device using a compact disc (CD) ROM storing the moving image data as a medium. system.