Moving picture coding, coded-moving picture bitstream conversion and coded-moving picture bitstream multiplexing

• US 6,954,499 B2
• Filed: 03/15/2001
• Issued: 10/11/2005
• Est. Priority Date: 03/15/2000
• Status: Active Grant

• Current Assignee: JVC Kenwood Corporation
• Original Assignee: Victor Company of Japan Limited (JVC Kenwood Corporation)
• Inventors: Sugiyama, Kenji
• Primary Examiner(s): DIEP, NHON THANH
• Application Number:
  US09/812,784
• Publication Number:
  US 20010026589A1
• Time in Patent Office: 1,671 Days
• Field of Search: H04/N00.7/12, 375/240.13, 375/240.25, 375/240.02, 375/240.07, 375/240.08, 375/240.15, 375/240.21, 375/240.12, 382/232, 382/236, 382/238
• US Class Current: 375/240.13
• CPC Class Codes: H04N 19/105 Selection of the reference unit for prediction within a chosen coding or prediction mode, e.g. adaptive choice of position and number of pixels used for prediction
• CPC Class Codes: H04N 19/126 Details of normalisation or weighting functions, e.g. normalisation matrices or variable uniform quantisers
• CPC Class Codes: H04N 19/132 Sampling, masking or truncation of coding units, e.g. adaptive resampling, frame skipping, frame interpolation or high-frequency transform coefficient masking
• CPC Class Codes: H04N 19/137 Motion inside a coding unit, e.g. average field, frame or block difference
• CPC Class Codes: H04N 19/15 by monitoring actual compressed data size at the memory before deciding storage at the transmission buffer
• CPC Class Codes: H04N 19/152 by measuring the fullness of the transmission buffer
• CPC Class Codes: H04N 19/159 Prediction type, e.g. intra-frame, inter-frame or bidirectional frame prediction
• CPC Class Codes: H04N 19/172 the region being a picture, frame or field
• CPC Class Codes: H04N 19/503 involving temporal prediction adaptive coding with adaptive selection between spatial and temporal predictive coding H04N19/107; adaptive coding with adaptive selection among a plurality of temporal predictive coding modes H04N19/109
• CPC Class Codes: H04N 19/577 Motion compensation with bidirectional frame interpolation, i.e. using B-pictures
• CPC Class Codes: H04N 19/587 involving temporal sub-sampling or interpolation, e.g. decimation or subsequent interpolation of pictures in a video sequence
• CPC Class Codes: H04N 19/61 in combination with predictive coding
• CPC Class Codes: H04N 21/234381 by altering the temporal resolution, e.g. decreasing the frame rate by frame skipping
• CPC Class Codes: H04N 21/2365 Multiplexing of several video streams
• CPC Class Codes: H04N 21/2401 Monitoring of the client buffer
• CPC Class Codes: H04N 21/2662 Controlling the complexity of the video stream, e.g. by scaling the resolution or bitrate of the video stream based on the client capabilities
• CPC Class Codes: H04N 21/4347 Demultiplexing of several video streams

Abstract

First pictures, set at a predetermined interval, to be used as reference pictures for inter-picture prediction of an incoming moving picture and second pictures different from the first pictures are coded. The first pictures are coded by intra-picture coding or unidirectional inter-picture predictive coding. The second pictures are coded by bidirectional inter-picture predictive coding using the first pictures or locally-decoded pictures of the first pictures as the reference pictures, to obtain a moving-picture bitstream. Motion activity is obtained on the incoming moving picture. The moving-picture bitstream is multiplexed with the information of motion activity. An incoming first moving-picture bitstream having bitstreams of the first and the second pictures coded as above at a first code transfer rate is converted into a second moving-picture bitstream at a second code transfer rate. Motion activity is obtained on the incoming first moving-picture bitstream. A decimation rate is set on the second pictures of the incoming first moving-picture bitstream according to at least the motion activity. The bitstreams of the second pictures are only decimated from the incoming first moving-picture bitstream at another predetermined interval according to the decimation rate. A plurality of incoming first moving-picture bitstreams are multiplexed into a moving-picture bitstream at a bit rate lower than a total bit rate of the incoming first moving-picture bitstreams. Each incoming first moving-picture bitstream has first moving-picture bitstreams of the first and the second pictures coded as above. A code amount of the multiplexed bitstream is obtained for each reproduction period as virtual buffer occupancy. A decimation rate is set on the second pictures of the incoming first moving-picture bitstreams according to the virtual buffer occupancy. The bitstreams of the second pictures are decimated from the incoming first moving-picture bitstreams at a predetermined interval according to the decimation rate, to obtain second bitstreams. The second bitstreams are multiplexed to obtain the multiplexed bitstream.

Claims

1. A bitstream conversion apparatus comprising:

a bitstream receiver to receive an incoming first moving-picture bitstream at a first code transfer rate in which the incoming first moving-picture bitstream has already been obtained by coding first pictures set at a predetermined interval and used as reference pictures for inter-picture prediction of a moving picture to be coded and coding second pictures different from the first pictures;

a motion amount detector to obtain motion activity from information on activity carried by the incoming first moving-picture bitstream;

a decimation controller to set a decimation rate on the second pictures of the incoming first moving-picture bitstream according to at least the motion activity; and

a bitstream decimator to decimate only bitstreams of the second pictures from the incoming first moving-picture bitstream at another predetermined interval according to the decimation rate, thus outputting a second moving-picture bitstream at a second code transfer rate different from the first code transfer rate.

2. A bitstream conversion method comprising the steps of:

receiving an incoming first moving-picture bitstream at a first code transfer rate in which the incoming first moving-picture bitstream has already been obtained by coding first pictures set at a predetermined interval and used as reference pictures for inter-picture prediction of a moving picture to be coded and coding second pictures different from the first pictures;

obtaining motion activity from information on activity carried by the incoming first moving-picture bitstream;

setting a decimation rate on the second pictures of the incoming first moving-picture bitstream according to at least the motion activity;

decimating only bitstreams of the second pictures from the incoming first moving-picture bitstream at another predetermined interval according to the decimation rate; and

outputting a second moving-picture bitstream at a second code transfer rate different from the first code transfer rate.