JP4289055B2 - Transcoder and recording / reproducing apparatus using the same - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a transcoder for converting a stream compression coding system and a recording / reproducing apparatus using the transcoder.
[0002]
[Prior art]
A variety of devices use a technique in which image information is digitized, compressed and encoded by an MPEG video compression technique, and recorded on a storage medium, or transmitted via a communication medium. For example, application examples include a DVD recording / reproducing apparatus using the MPEG-2 Video (ISO / IEC 13818-2) system and communication between portable terminals using the MPEG-4 Video (ISO / IEC 14496-2) system. As described above, as a result of the different compression methods depending on the application, the degree of demand for transcoding technology for converting data between different compression encoding methods is increasing in each device. For example, Patent Document 1 discloses a technique for transcoding from MPEG-2 to MPEG-4.
[0003]
[Patent Document 1]
Japanese Patent Laid-Open No. 2000-92497
In Patent Document 1, transcoding between MPEG video streams is realized by once decoding an MPEG video stream and encoding it again using another MPEG video compression encoding method. At this time, a method is employed in which the decoded image of the MPEG is temporarily generated in the order of encoding instead of the display order and converted into the other MPEG video, thereby reducing the processing delay at the time of transcoding. In general, when implementing a transcoding device, the decoding unit often has the same configuration as a decoding device that decodes an MPEG video stream and outputs it as a video signal. The video signal is converted into an external synchronization signal for each frame. In many cases, they are output together and encoded again using an encoding device.
[0005]
[Problems to be solved by the invention]
Although the technique disclosed in Patent Document 1 shortens the transcoding processing delay, the transcoding processing time is not significantly shortened. That is, when transcoding is performed on the basis of a decoding circuit, a time equivalent to decoding the input stream and outputting the video is required for transcoding. I had to wait a long time. An object of the present invention is to shorten the transcoding time in view of the above situation and improve the usability of the transcoder.
[0006]
[Means for Solving the Problems]
In order to solve the above-described problem, the apparatus of the present invention has a first operation mode that decodes the first stream and outputs a decoded image in synchronization with the rate displayed on the external device, and high speed without synchronizing with the display rate. Has a second operation mode for transcoding. Further, the second operation mode has a GUI for displaying the progress status of the transcoder. Further, it has a function of thinning and displaying an image in the middle of transcoding during the second operation mode.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a block diagram showing a first embodiment of a video recording / reproducing apparatus including a transcoder according to the present invention. This apparatus is an example of a video recording / reproducing apparatus that records an imaging signal as an MPEG2 video stream on a storage medium, and reproduces and outputs the stream from the storage medium. This video recording / reproducing apparatus has a function of decoding and outputting the reproduced MPEG2 stream, and a function of converting the reproduced MPEG2 video stream into an MPEG4 video stream and outputting the same to the outside. This will be described with reference to the drawings.
[0008]
When recording an imaging signal on the medium 100, a recording instruction is issued from the user IF 109, and in response to this, the MPEG2 stream generation unit 300 controls the lens unit 301 and the signal processing circuit 302 to convert the captured analog signal into digital video. Convert to signal. Further, the digital video signal is encoded by the MPEG2 encoder 303 to generate an MPEG2 video stream. The MPEG2 video stream is recorded on the storage medium 100 via a media IF (recording / reproducing circuit) 101 together with audio information (not shown) or video stream management data.
[0009]
When a reproduction instruction is given by the user IF 109, a predetermined stream portion of the MPEG2 video stream recorded on the medium 100 is reproduced from the medium 100. The reproduced video stream is sent to the MPEG2 / 4 transcoder 200 via the media IF 101. The MPEG2 decoder 201 in the transcoder 200 decodes the MPEG2 video stream and generates pixel value data of the digital video signal. Each pixel data is read by the display circuit 104 in synchronization with a synchronizing signal for display on an external display device, and is output to a display device connected to the terminal 105.
[0010]
FIG. 2 is a diagram showing the relationship between the decoding operation and the display frame. Here, as shown in 801 to 806, the MPEG2 stream is encoded with information for each frame divided into picture types called I, P, and B pictures according to the motion compensation method with other frames. According to the MPEG standard, an I picture is encoded using information in its own picture without using information of other frames, and a P picture refers to information of a picture that is older in display order than its own picture. The pictures and B pictures that are encoded by the compensation are motion compensated by referring to the information of the I or P picture before the own picture in the display order and the I or P picture after the display order. Defined as a picture to be encoded.
[0011]
In the example of FIG. 2, since the B pictures 802 and 803 refer to the information of the I picture 801 that is later in the display order, the I picture 801 is encoded in an earlier order than the B pictures 802 and 803, and is decoded. As shown in the row of the frame being decoded, the I picture 801 is ahead of 802 and 803. Since the decoded images are returned and displayed in the original display order, they are rearranged in the frame order as shown in the post-decode display timing row and displayed in the order of 812, 813, 814, 815, and 817. At this time, for example, when displaying an image on an NTSC interlaced display device, if each picture image is a frame image, the information of each frame corresponds to a signal for two fields and is synchronized with the vertical synchronization signal of each field. Thus, pixel data is read out and output from the display circuit 104 during a predetermined effective pixel region period. In order to output to the external display as described above, the decoded images 801 to 806 are temporarily stored in the frame memory 202 of FIG. 1 and held until displayed. In order to prevent overflow of the frame memory necessary for holding, decoding is performed by controlling the display speed to be the same as the average display speed. In the case of FIG. 2, the decoding and display timings are shifted, but both have a frame memory 202 for a fixed number of frames in order to perform processing at the rate of one frame for each frame in synchronization with the vertical synchronization period. It is possible to perform processing.
[0012]
Next, a case where an MPEG2 stream is converted into an MPEG4 stream will be described. In the block diagram of FIG. 1, the MPEG4 encoder 203 receives the image data decoded by the MPEG2 decoder 201 and re-encodes it as an MPEG4 stream, thereby converting (transcoding) from MPEG2 to MPEG4. The converted MPEG4 video stream is output to the outside from the terminal 103, and is output to a network by an external communication IF (not shown) or recorded on another storage medium. In MPEG4 encoding, as in MPEG2, each input image frame is encoded as one of I, P, and B pictures.
[0013]
FIG. 3 shows the operation timing when transcoding from MPEG2 to MPEG4 in FIG. In this embodiment, since the image in transcoding is not displayed on an external display device, it is not necessary to proceed with decoding at the same rate as the external display rate as shown in FIG. Therefore, each frame is decoded at the fastest speed within the range allowed by the hardware specifications. The time required for decoding each frame varies depending on the code amount of each frame, the complexity of the motion compensation process, etc., and is variable as indicated by reference numerals 901 to 906 in FIG. In general, due to improvements in the processing capabilities of hardware and software, MPEG2 decoding of one frame can be processed faster than the time required for the display period of each frame (two field periods). It is possible to generate a decoded image faster than the time. Also, the bit rate that can be read from the storage medium 100 is sufficiently high compared to the bit rate of the MPEG2 video stream, and even when decoding processing is performed at high speed, the stream is supplied via the media IF 109 at a bit rate corresponding to that. Is possible. On the other hand, MPEG4 encoding is performed at the timing when decoding of each frame of MPEG2 is completed (701 to 706 in FIG. 3), with the MPEG2 decoded image of that frame being input. Similarly, each frame 911 to 916 of MPEG4 encoding is processed at a high speed as long as the processing capability of the hardware permits, and when the encoding of the next frame is completed, the next processing start is waited until the decoding start time 701 to 706.
[0014]
In the present embodiment, an example in which the encoding process of each frame is shorter in MPEG4 than in MPEG2 is shown. However, when the frame processing in MPEG2 is shorter, the MPEG2 side waits for the end of the corresponding frame processing in MPEG4 and waits for the next. Frame processing may be performed. For example, in the case of 904 and 913 frames, if the processing time encoding time of 913 is longer, the timing of 704 is adjusted so that the processing of 905 is started after the end of 913. When transcoding is performed as described above, since each frame is not output in synchronization with an external display device, it can be transcoded faster than normal MPEG2 decoding and playback processing. Also, as shown in FIG. 3, when the start timing of decoding and encoding does not coincide with each other for each frame and MPEG2 and MPEG4 have completely different start timings and the frame memory is likely to overflow, the MPEG2 encoding is stopped and the frame memory When an underflow is likely to occur, it can be realized by a method of performing MPEG4 encoding processing.
[0015]
Further, during the transcoding period, for example, as shown in FIG. 4, the display circuit 104 performs OSD processing, and informs the user of the progress status of the transcoding, thereby predicting the waiting time. As described above, when the normal IF2 decoding / playback process and the transcoding process to MPEG4 are changed as instructed by the user IF 109, the function of adaptively changing the MPEG2 decoding process rate according to the situation is provided. Realize both movements without failure.
[0016]
FIG. 5 shows a second embodiment according to the present invention. This embodiment has the same configuration as the first embodiment and transcode processing is performed in the same manner, but has a function of sampling and displaying a part of the image in the transcode from MPEG2 to MPEG4. For example, by causing the display circuit 104 to process so as to hold and output only one MPEG2 video frame decoded by the MPEG2 decoder 201, the MPEG2 decoding process is in progress as shown at 921 and 927 in FIG. It becomes possible to output a specific frame. In FIG. 5, each time each I picture is decoded, the display circuit takes it in and repeats the display every frame until the next I picture is decoded. As a result, the user can check the outline of the progress of transcoding by the design, and can roughly predict the waiting period for completion of transcoding. Further, as in the first embodiment, the transcoding process does not need to match the MPEG2 decoding process of each frame to the rate of the external display circuit, and thus can be processed at high speed. Such a process can be realized, for example, by a configuration in which MPEG2 decoded images for 921 and 927 sample display frames in FIG. 5 are saved and held in the frame memory 202 in FIG.
[0017]
FIG. 6 shows a third embodiment according to the present invention. In the present embodiment, the input image obtained as the captured image is encoded in the first embodiment, but an external broadcast signal or the like is received, a necessary stream is selected and recorded, and then reproduced. And a video recording / reproducing apparatus that enables transcoding. When a channel selection signal and a reception instruction are issued from the user IF 109 to the receiving portion 400, an MPEG2 stream obtained via a wired or wireless network is input from the input terminal 401. This is demodulated by the demodulation circuit 402 and subjected to packet separation processing in the packet separation circuit 403, whereby an MPEG2 stream for a desired channel is obtained. The extracted MPEG2 stream is recorded on a storage medium 100 such as an HDD or an optical disk via the media IF 101. The recorded data can be reproduced and displayed as in the first embodiment, and can be transcoded to MPEG4.
[0018]
In each of the above embodiments, the video signal has been described, but the present invention can be similarly applied to an audio signal and various data signals. The compression encoding method has been described on the premise of conversion processing between MPEG2 and MPEG4. It goes without saying that the present invention is also effective when other compression encoding methods such as H.263 are used.
[0019]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to this invention, the waiting time of a transcode process can be shortened and a user's usability can be improved.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a first embodiment of a video recording / reproducing apparatus according to the present invention.
FIG. 2 is a diagram showing MPEG2 decoding processing timing in the embodiment of FIG. 1;
FIG. 3 is a diagram showing transcode processing timing from MPEG2 to MPEG4 in the embodiment of FIG. 1;
FIG. 4 is a diagram showing an OSD screen of the progress status during transcoding.
FIG. 5 is a diagram showing sample screen display timing of the second embodiment of the video recording / reproducing apparatus according to the present invention;
FIG. 6 is a block diagram showing a third embodiment of a video recording / reproducing apparatus according to the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 100 ... Storage medium 1, 101 ... Media IF, 103 ... MPEG4 stream output terminal, 104 ... Display circuit, 105 ... Reproduction video output terminal, 109 ... User IF, 200 ... MPEG2 / 4 transcoder, 201 ... MPEG2 decoder, 202 ... Frame memory 203... MPEG4 encoder 300. MPEG2 video stream generation unit 301. Lens unit 302. Signal processing circuit 303. MPEG2 encoder 400 400 broadcast signal reception unit 401 reception terminal 402 demodulation circuit 403 ... Packet separation

Claims (6)

In a transcoder that converts a first stream that has been compression-encoded using a first compression-encoding scheme into a second stream that has been compression-encoded using a second compression-encoding scheme,
Decoding means for decoding the first stream;
Output means for outputting the decoded signal to an external device;
Encoding means for encoding the decoded signal to generate the second stream ;
The decoding means and the output means, the first stream in synchronization with the rate to be displayed on the external device, a first operation mode and output the decoded, the decoding means and the encoding means , without synchronizing the rate that makes the display by the external device, by a second operation mode for encoding is decoded faster than the rate control and the decoding means and the output means and the encoding means Control means to
Transcoder, characterized in that it comprises a.   2. The transcoder according to claim 1, wherein when instructed by a user to play back the first stream, processing is performed in the first operation mode, and from the first stream to the second stream from the user. A transcoder characterized by processing in the second operation mode when instructed to transcode to a stream.   2. The transcoder according to claim 1, further comprising a GUI for displaying a progress status of the transcoder in the second operation mode.   2. The transcoder according to claim 1, wherein the output means has a function of outputting a part of a signal in the middle of transcoding to the external device during the second operation mode. . A recording / reproducing apparatus using the transcoder according to any one of claims 1 to 4,
Imaging means for imaging a subject, second encoding means for encoding an image signal from the imaging means by the first compression encoding method, and a first stream generated by the second encoding means A recording / reproducing apparatus comprising: recording means for recording the data on a storage medium; and reproduction means for reproducing the first stream from the storage medium. A recording / reproducing apparatus using the transcoder according to any one of claims 1 to 4,
And a receiving means for receiving the first stream from outside, a recording means for recording the received first stream on a storage medium, and a playback means for playing back the first stream from the storage medium. Recording / playback device.

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