WO2006072543A1 - Device and method for video data recording - Google Patents

Device and method for video data recording Download PDF

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Publication number
WO2006072543A1
WO2006072543A1 PCT/EP2005/056867 EP2005056867W WO2006072543A1 WO 2006072543 A1 WO2006072543 A1 WO 2006072543A1 EP 2005056867 W EP2005056867 W EP 2005056867W WO 2006072543 A1 WO2006072543 A1 WO 2006072543A1
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WO
WIPO (PCT)
Prior art keywords
image
stream
images
mapping
storage
Prior art date
Application number
PCT/EP2005/056867
Other languages
French (fr)
Inventor
Sylvain Fabre
Frédéric Pasquier
Bruno Garnier
Original Assignee
Thomson Licensing
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Thomson Licensing filed Critical Thomson Licensing
Publication of WO2006072543A1 publication Critical patent/WO2006072543A1/en

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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N5/00—Details of television systems
    • H04N5/76—Television signal recording
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B27/00—Editing; Indexing; Addressing; Timing or synchronising; Monitoring; Measuring tape travel
    • G11B27/005—Reproducing at a different information rate from the information rate of recording
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N5/00—Details of television systems
    • H04N5/76—Television signal recording
    • H04N5/78—Television signal recording using magnetic recording
    • H04N5/782—Television signal recording using magnetic recording on tape
    • H04N5/783—Adaptations for reproducing at a rate different from the recording rate
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B2220/00—Record carriers by type
    • G11B2220/20—Disc-shaped record carriers
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B2220/00—Record carriers by type
    • G11B2220/20—Disc-shaped record carriers
    • G11B2220/25—Disc-shaped record carriers characterised in that the disc is based on a specific recording technology
    • G11B2220/2508—Magnetic discs
    • G11B2220/2516—Hard disks
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B2220/00—Record carriers by type
    • G11B2220/40—Combinations of multiple record carriers
    • G11B2220/45—Hierarchical combination of record carriers, e.g. HDD for fast access, optical discs for long term storage or tapes for backup
    • G11B2220/455—Hierarchical combination of record carriers, e.g. HDD for fast access, optical discs for long term storage or tapes for backup said record carriers being in one device and being used as primary and secondary/backup media, e.g. HDD-DVD combo device, or as source and target media, e.g. PC and portable player
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N5/00—Details of television systems
    • H04N5/76—Television signal recording
    • H04N5/78—Television signal recording using magnetic recording
    • H04N5/781—Television signal recording using magnetic recording on disks or drums
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N9/00—Details of colour television systems
    • H04N9/79—Processing of colour television signals in connection with recording
    • H04N9/80—Transformation of the television signal for recording, e.g. modulation, frequency changing; Inverse transformation for playback
    • H04N9/804—Transformation of the television signal for recording, e.g. modulation, frequency changing; Inverse transformation for playback involving pulse code modulation of the colour picture signal components
    • H04N9/8042—Transformation of the television signal for recording, e.g. modulation, frequency changing; Inverse transformation for playback involving pulse code modulation of the colour picture signal components involving data reduction

Abstract

The invention relates to a method and a device for recording a stream of encoded video images, images being coded in a dependent manner such that the coding of a first image is used to code a second image, the choice of the mode of coding being decided by the encoder. The device comprises means of storage (1) intended to record the stream and means (2) to establish a mapping of the stream making it possible to index the images recorded in the means of storage (1).

Description

DEVICE AND METHOD FOR VIDEO DATA RECORDING
The invention relates to a device and a procedure for recording video data.
The invention relates more particularly to devices for recording compressed data.
The use of special modes of navigation ("trickmodes") in devices for recording compressed data requires a knowledge of the structure of the stream so as to play the stream back in a reverse order or at an accelerated or slowed speed.
Certain modes of data compression, such as MPEG-2, provide for a data structure organized as a group of images ("GOP" standing for group of pictures), whose coding structure is known and fixed. The images may be coded according to three different modes:
- a category of so-called intra images (I), an intra image being decodeable and displayable without requiring the decoding of another image. - a category of so-called predictive images (P), a predictive image requiring the decoding of the intra or predictive image transmitted prior to this predictive image so as to be displayed, and
- a category of so-called bi-predictive images (B), a bi-predictive image requiring the decoding of the images displayed before and subsequent to this by-predictive image so as to be displayed.
The emergence of the H264 standard is giving rise to new problems in the management of special navigation modes. In particular, this standard does not prescribe the structure in terms of organization of the types of images in a GOP. This implies that when the stream is to be played back in a special mode, the images cannot be decoded fast enough since their inter-dependence is not known and hence it is necessary to decode them all. A conceivable solution is to dimension the system in such a way that it is capable of decoding all the images recorded on the hard disk 1 in fast forward or rewind modes. This represents an expensive solution in respect of embedded systems of digital decoder type.
Another solution would consist in decoding the images in tandem with their recording and thus in not recording the images in compressed mode.
This represents a very expensive solution in terms of memory capacity. A decoded high-definition image (HD) involves around 3.2 MB; to save a minute of film at 25 images per second, a hard disk of 80 MB is required.
Accordingly, the invention proposes a device for recording a stream of encoded video images, images being coded in a dependent manner such that the coding of a first image is used to code a second image, the choice of the mode of coding being decided by the encoder, the device comprising means of storage intended to record the stream.
According to the invention the device comprises means to establish a mapping of the stream making it possible to index the images recorded in the means of storage.
The invention can therefore make it possible to perform special modes of navigation, the mapping making it possible to ascertain the structure of the data and hence to decode the images faster, by decoding only the images required for the displaying of certain images.
According to a preferred embodiment, the means to establish the mapping establish it prior to the recording of the video images in the means of recording.
Advantageously, the device comprises - means of reading of the stream - means to extract, for each image at least one so-called reference cue indicating whether the said image is a reference image serving for the coding of the other images.
In a preferred manner, the means to establish the mapping establish a table comprising for each image the number of the image in the stream and the said reference cue.
Preferably, the device comprises means to record the mapping in the means of storage when the stream is recorded.
Advantageously, the device comprises means of decoding of the stream according to at least one special navigation mode.
According to a preferred embodiment, the device comprises
- means of readout of the stream recorded in the means of storage,
- means of readout of the mapping associated with the stream read in the said means of storage, the means of decoding performing the decoding of the said stream read in the means of storage as a function of the said associated mapping.
The invention also relates to a method for recording a stream of encoded video images, images being coded in a dependent manner such that the coding of a first image is used to code a second image, the choice of the mode of coding being decided by the encoder, the device comprising means of storage intended to record the stream.
According to the invention, the method establishes a mapping of the stream making it possible to index the images recorded in the means of storage.
The invention will be better understood and illustrated by means of wholly nonlimiting advantageous modes of implementation and embodiment, with reference to the appended figures in which: - Figure 1 represents an exemplary device according to the invention,
- Figure 2 represents a sequence of dependent images,
- Figure 3 represents a flowchart of the operation of the reception module 2.
The modules represented are functional units, which may or may not correspond to physically distinguishable units. For example, these modules or some of them may be grouped together into a single component, or constitute functionalities of one and the same piece of software. Conversely, certain modules may possibly be composed of separate physical entities.
The preferred embodiment illustrated hereinbelow is based on a stream in accordance with the H264 standard but the invention is not limited to this standard and may be applied to MPEG-2 type streams or other streams whose structure is not known.
The device according to Figure 1 is for example included in an appliance of digital decoder type, commonly referred to as a "digital set-top box". This device is able to receive streams of various nature and in particular streams of MPEG-2 type or those in accordance with the H264 standard.
An H264 or MPEG-2 stream is received by a reception module 2. This stream emanates from a transmitter and may be a television type stream.
The reception module 2 steers the stream as a function of its type and as a function of the application (recording or direct viewing).
The reception module decodes the header to detect the type of stream, MPEG-2 or H264. The reception module 2 is informed of the application by a master module 7 which receives information for example from a user interface, not represented. The user interface may allow the user to inform the device if he wishes to record a programme or if he prefers to view it directly. The MPEG-2 type streams are steered to an MPEG-2 decoding module 4 or to a storage module 1. The storage module 1 is a hard disk. In other embodiments, it may also be a CDROM, a DVD, a memory card or any other type of storage.
The H264 type streams are steered to an entropy decoding module 8 or to the hard disk 1.
The MPEG-2 and H264 streams received by the reception module 2 are steered respectively to the modules 4 and 8 when they are intended for direct display, without prior storage. This is the conventional case of viewing of an audiovisual programme.
The reception module 2 steers the MPEG-2 and H264 streams as a function of their header.
The invention relates more precisely to the embodiment in which the streams are previously recorded on the hard disk 1 before the viewing thereof.
Recording mode
MPEG-2 stream
When an MPEG-2 type stream is detected by the reception module 2, the stream is sent to the hard disk 1. The data are recorded in the hard disk 1 in such a way as to be able to be played back subsequently according to various modes of navigation or quite simply by conventional reading.
Procedures known to the person skilled in the art make it possible to play back MPEG-2 streams according to special modes of navigation. An MPEG-2 type stream has a known structure, the reference images being known and fixed by the norm.
H264 stream When the reception module 2 receives an H264 type stream for recording on the hard disk 1 , it constructs a mapping for this stream.
The data in the H264 stream are coded in an order established by the coding device and not in an identical manner for all the groups of images.
A stream in accordance with the H264 standard is composed of a series of compressed images each having a specified type.
The images are stored linearly in the stream in the form of autonomous units called NALs (the acronym standing for "Network Abstraction Layers").
An image is associated with each NAL.
In the H264 standard, in addition to the images of type I, B and P, there are images of type IDR. The IDR type images are intra images but which indicate that all the images of type P or B following this IDR image do not make any use of images decoded before this IDR image. Consequently, IDR images are inserted regularly into the stream to provide points of access when starting up a coder or when hopping.
The images of type B and P are images coded in predictive mode and therefore need reference images in order to be decoded.
To decode an image of P type, the previous reference images must have been decoded before. A reference image is an image on which other images are based. The I images and the IDR images are images coded in intra mode and consequently need no reference image to be decoded. To decode an image of type B, previous images and subsequent images must be decoded.
The H264 standard specifies the maximum number of reference images supported, as a function of defined profiles. Such an example of coding dependence is illustrated with reference to Figure 2.
The H264 standard codes the images in the GOPs, not always using the same reference images. When a GOP is received by the device, the device does not know the dependencies of the various images. For each image, the NAL indicates the images of the GOP that are necessary for the decoding thereof.
The reception module therefore establishes a mapping of the stream received. The images received by the reception module 2 are sent in tandem with their reception in the hard disk 1. Once all the images of the stream have been received, the mapping is in turn recorded on the hard disk 1. This is illustrated in Figure 3.
Mode of decoding of the H264 stream for special navigation modes
When one wishes to view the data recorded on the hard disk 1 according to a particular mode of navigation, for example fast forward or fast rewind or slow motion, the associated data and mapping are read in the hard disk 1 by a transfer module 3.
A master processor 7 sends the transfer module 3 the desired mode of display, either fast forward or rewind, or slow motion or other special modes of navigation.
The transfer module 3 then loads the mapping associated with the data stream to be transferred.
Fast forward times 2 mode
In the case of a fast forward mode, with a speed of display twice as high as normal, the display module displays the images IDR0, B2, P4, Pe- To do this, the transfer module sends the following images to the entropy decoding module:
- the image IDR0
- the image B2 and the image P4 which together with the image IDR0 serves to decode the image B2,
- the image Ps which is decoded with respect to the image P4 and to the image IDR0.
Fast rewind times 2 mode
In the case of a rewind mode with a speed of display twice as high as normal, the display module therefore requires one image out of two. It therefore displays the images P8, P4, B2, IDR0.
To do this, the transfer module sends the following images to the entropy decoding module:
- the image P8 which is decoded with respect to the image P4 and to the image IDR0,
- the image P4 which is decoded with respect to the image IDR0, - the image IDR0,
- the image B2 which together with the image IDR0 serves to decode the image B2.
Thus, for each image to be displayed, the reading of the mapping advantageously makes it possible to decode only the images required for the decoding of the images to be displayed and thus may make it possible to economize on resources in terms of calculation power so as to display the images fast enough, particularly in fast forward or fast rewind mode where the images must be decoded rapidly. The images not displayed and which do not serve as reference are therefore not read into memory.
The entropy decoding module 8 performs a decoding of the data received from the transfer module 3. Thereafter the data decoded by the entropy decoding module 8 are sent to a pixel decoding module 10. The pixel decoding module 10 decodes the data received from the entropy decoding module 8.
The data are thereafter transferred to a memory of DDRAM type 9 allowing temporary storage of the images before display.
Mode of decoding of the H264 stream for the normal mode of reading
The normal mode of reading is a mode which requires no reading of the mapping. In fact, all the images being displayed, they must all be decoded. During this mode of reading, all the images are read from the hard disk 1 by the transfer module 3 and transferred to the entropy decoding module 8. The data are thereafter transferred to the pixel decoding module 10.
The data are thereafter transferred to the display module 6 by way of the DDRAM type memory 9 allowing temporary storage of the images before display.
Direct mode of display (without prior recording)
MPEG-2 stream
During the reception of an MPEG-2 stream which is to be viewed directly, the stream is sent by the reception module 2 to an MPEG-2 decoding and audio decoding module 4. The decoding module 4 is a conventional decoder in accordance with the MPEG-2 standard. This module 4 sends the decoded data to a viewing module 5 which sends them to a display device such as a screen.
H264 stream During the reception of a stream in accordance with the H264 standard that is to be viewed directly and not saved on the hard disk 1 for subsequent viewing, the data are sent by the reception module to the entropy decoding module 8.
All the images are therefore sent to the entropy decoding module 8 and decoded thereafter as described previously in respect of the recording mode.
Figure 2 represents a series of images constituting a GOP.
The order of the images represents the order of display of the images but represents neither the order of decoding nor the order of sending of the images.
The order of display is as follows:
IDR0, B1, B2, B3, P4, B5, B6, B7, P8, IDR9
The series of images comprises a first image IDR0 coded in IDR mode. It constitutes a reference image for other images.
The image IDR0 is followed by an image Bi coded in bi-predictive mode. Bi has as reference image the image IDR0, the image B2 and the image P4.
The image Bi is followed by an image B2 coded in bi-predictive mode.
B2 has as reference image the image IDR0 and the image P4.
The image B2 is followed by an image B3 coded in bi-predictive mode. B3 has as reference image the image IDR0, B-i, B2 and P4.
The image B3 is followed by an image P4 coded in bi-predictive mode. P4 has as reference the image IDR0. The images B5, B6, B7 following the image P4 do not serve as reference images for the other images.
B5 is coded in bi-predictive mode and has as reference image the image P4 and the image P8.
B6 is coded in bi-predictive mode and has as reference the images B5 and P8.
B7 is coded in bi-predictive mode and has as reference the images B5 and P8.
The image B7 is followed by an image P8 coded in predictive mode and having as reference image the image P4 and the image IDR0.
The image P8 is followed by an image IDRg coded in intra mode and terminating the GOP.
The order of decoding and of sending of the images is as follows: IDR0, P4, B2, B1, B3, P8, B5, B6, B7, IDR9.
The mapping contains the list of images of the stream.
The mapping is represented physically in the form of a table with two columns. The left column gives the image number in the stream. The right column records for each image received, the first 40 bits of the NAL.
These first 40 bits are represented hereinbelow:
Figure imgf000013_0001
Table 1
The mapping given as an example is a very simple mapping. In other embodiments, it is possible to associate more information with each image.
This gives for the GOP illustrated in Figure 2 the following values:
Figure imgf000014_0001
Table 2
Bit 10 indicates whether an image is a reference image.
Bits 0 to 8 indicate for each image, the reference images. When the corresponding bit is set to one, then the corresponding image is a reference image for the image considered.
Figure 3 represents a flowchart of the operation of the module 2 during the reception of an H264 data stream.
During a step E1 , it reads the first 40 bits of the first NAL of the stream. It then performs a test (step E2) to ascertain whether this NAL is an NAL of image type.
If this NAL is an NAL of image type, then it writes to the mapping, the number of the image in the stream and the first 40 bits of this NAL during a step E3.
If this NAL is not an NAL of image type, then it records the NAL on the hard disk without modifying the mapping during a step E5.
It also performs a decoding at the block level up to the entropy so as to recover for each image, the reference images with respect to which this image is coded.
After step E3, it goes to step E4 in which it increments the image counter so as to write to the next box of the mapping for the following image received.
Thereafter, during a step E5, it performs a test during a step E6 in such a way as to ascertain whether the stream has been received in its entirety.
If such is the case, it then goes to step E7, otherwise it goes to step E1.
During step E7, it records the NAL corresponding to the stream on the hard disk 1.
After step E7, we go back to step E1 in which we wait for a new NAL.

Claims

Claims
1. Device for recording a stream of encoded video images, images being coded in a dependent manner such that the coding of a first image is used to code a second image, the choice of the mode of coding being decided by the encoder, the device comprising means of storage (1 ) intended to record the stream characterized in that it comprises means (2) to establish a mapping of the stream making it possible to index the images recorded in the means of storage (1 ).
2. Device according to Claim 1 , characterized in that the means (2) to establish the mapping establish it prior to the recording of the video images in the means of recording.
3. Device according to Claim 1 or 2, characterized in that it comprises
- means (2) of reading of the stream
- means (2) to extract, for each image at least one so-called reference cue indicating whether the said image is a reference image serving for the coding of the other images.
4. Device according to Claim 3, characterized in that the means to establish the mapping establish a table comprising for each image the number of the image in the stream and the said reference cue.
5. Device according to one of the previous claims, characterized in that it comprises means (2) to record the mapping in the means of storage (1 ) when the stream is recorded.
6. Device according to Claim 5, characterized in that it comprises means (8) of decoding of the stream according to at least one special navigation mode.
7. Device according to Claim 6, characterized in that it comprises
- means (3) of readout of the stream recorded in the means of storage (1 ),
- means (3) of readout of the mapping associated with the stream read in the said means of storage (1 ), the means (8) of decoding performing the decoding of the said stream read in the means of storage (1 ) as a function of the said associated mapping.
8. Method for recording a stream of encoded video images, images being coded in a dependent manner such that the coding of a first image is used to code a second image, the choice of the mode of coding being decided by the encoder, the device comprising means of storage (1 ) intended to record the stream characterized in that it establishes a mapping of the stream making it possible to index the images recorded in the means of storage (1 ).
PCT/EP2005/056867 2005-01-05 2005-12-16 Device and method for video data recording WO2006072543A1 (en)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102025992A (en) * 2010-11-23 2011-04-20 浙江大学 Reference-image management method for interframe predicting process in H.264 video decoding system

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EP0817480A1 (en) * 1995-03-20 1998-01-07 Matsushita Electric Industrial Co., Ltd. Device and method for recording picture information
US6002834A (en) * 1995-02-24 1999-12-14 Hitachi, Ltd. Optical disk having table relating sector address and time and optical disk reproducing apparatus
US6628890B1 (en) * 1999-01-27 2003-09-30 Matsushita Electric Industrial Co., Ltd. Digital recording/reproduction apparatus

Patent Citations (3)

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Publication number Priority date Publication date Assignee Title
US6002834A (en) * 1995-02-24 1999-12-14 Hitachi, Ltd. Optical disk having table relating sector address and time and optical disk reproducing apparatus
EP0817480A1 (en) * 1995-03-20 1998-01-07 Matsushita Electric Industrial Co., Ltd. Device and method for recording picture information
US6628890B1 (en) * 1999-01-27 2003-09-30 Matsushita Electric Industrial Co., Ltd. Digital recording/reproduction apparatus

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102025992A (en) * 2010-11-23 2011-04-20 浙江大学 Reference-image management method for interframe predicting process in H.264 video decoding system

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