Systems and methods for playing digital video in reverse and fast forward modes

• US 7,570,867 B2
• Filed: 10/10/2005
• Issued: 08/04/2009
• Est. Priority Date: 05/14/2001
• Status: Active Grant

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Microsoft Corporation
• Inventors: Green, Dustin L., Barrett, Peter T.
• Primary Examiner(s): Tran; Thai
• Assistant Examiner(s): Atala; Jamie Jo
• Application Number:
  US11/247,011
• Publication Number:
  US 20060029372A1
• Time in Patent Office: 1,394 Days
• Field of Search: 386 68- 80, 386 6- 8, 386111-112, 725 88- 90
• US Class Current: 386/344
• CPC Class Codes: H04N 5/781 on disks or drums
• CPC Class Codes: H04N 5/783 Adaptations for reproducing at a rate different from the recording rate
• CPC Class Codes: H04N 9/8045 using predictive coding

Abstract

Replaying a compressed digital video stream in fast-forward and reverse modes at varied playback rates. An index of intercoded frames, those frames not dependant on other frames for generation, is stored. The index includes the size of intercoded frames and their storage location. When a specified playback rate is requested, the intercoded frames are retrieved using the index. The intercoded frames then have one or more intracoded frames, frames that reference other frames for generation, placed between them to generate a frame sequence. The intracoded frames are “blank,” meaning they contain only information from their associated intercoded frame. By inserting “blank” frames specified playback rates and bit rates are generated. The index of intercoded frames may also be accessed to generate playback in reverse mode, which conserves memory resources of associated systems by generating the reverse playback stream in an iterative manner.

Claims

1. A system that includes an MPEG decoder and has access to a stored MPEG stream that includes I-frames, P-frames, and B-frames, the system being configured for implementing a method for displaying the stored MPEG stream in a reverse mode without requiring simultaneous buffering of all frames between temporally adjacent I-frames, the system comprising:

one or more computer-readable media having computer executable instructions for implementing the method, wherein the method comprises;

an act of buffering two temporally adjacent I-frames, including a first I-frame and a second I-frame that is temporally later in the stored MPEG stream;

based on the first I-frame, an act of iteratively reconstructing and buffering P-frames until a particular P-frame that is temporally adjacent to the second I-frame is reconstructed and buffered;

an act of displaying video data encoded in the second I-frame;

an act of reconstructing and displaying video data encoded in each B-frame between the reconstructed particular P-frame and the second I-frame in reverse order;

an act of displaying video data encoded in the reconstructed particular P-frame; and

act of iteratively reconstructing other P-frames and B-frames between the first I-frame and the particular reconstructed P-frame to continue displaying video data encoded in frames in the reverse sequence compared to the original sequence without simultaneously buffering all frames between the first I-frame and the second I-frame.

2. A system as recited in claim 1, wherein the act of iteratively reconstructing and buffering P-frames comprises an act of simultaneously buffering all P-frames.

3. A system as recited in claim 1, wherein the act of iteratively reconstructing and buffering P-frames comprises the following:

an act of reconstructing a temporally first P-frame after the first I-frame using the first I-frame;

an act of buffering the temporally first P-frame after the act of reconstructing the temporally first P-frame;

an act of releasing the buffer that stored the first I-frame after the act of buffering the temporally first P-frame; and

an act of repeating the acts of reconstructing, buffering and releasing for successive P-frames until the particular P-frame is buffered.

4. A system as recited in claim 1, wherein the MPEG decoder uses three needed buffers and “

m”

spare buffers, wherein the second I-frame is buffered in one of the three needed buffers, wherein the first I-frame is initially buffered in another of the three needed buffers initially leaving one empty needed buffer, wherein the act of iteratively reconstructing and buffering P-frames comprises the following;

an act of reconstructing a temporally first P-frame after the first I-frame using the first I-frame;

an act of buffering the temporally first P-frame after the act of reconstructing the temporally first P-frame;

an act of determining whether or not to copy the first I-frame into one of the “

m”

spare buffers;

an act of copying the first I-frame into one of the “

m”

spare buffers if it has been determined that the first I-frame is to be copied into one of the “

m”

spare buffers;

an act of releasing the buffer that stored the first I-frame after the act of determining whether or not to copy the first I-frame into one of the “

m”

spare buffers;

an act of determining whether or not to copy the first P-frame into one of the “

m”

spare buffers;

an act of copying the first P-frame into one of the “

m”

spare buffers if it has been determined that the first P-frame is to be copied into one of the “

m”

spare buffers; and

an act of repeating the acts of reconstructing, buffering, determining and releasing for successive P-frames until the particular P-frame is buffered.

5. A system as recited in claim 4, wherein the act of determining whether or not to copy the first P-frame into one of the “

m”

spare buffers comprises the following;

an act of determining that the first P-frame is to be copied into one of the “

m”

spare buffers if any of the following conditions are true;

the first P-frame is temporally at least 1/(1+n)th of the way from the temporally last frame stored in the spare buffers to the temporally last frame stored in the needed buffers, where “

n”

is the number of unused spare buffers;

or

there is only one P-frame between the first P-frame and the temporally last frame in the needed buffers.

6. A system as recited in claim 5, further comprising repeating the act of determining that the first P-frame is to be copied into one of the “

n”

spare buffers, for all other P-frames temporally later than the first P-frame, but temporally earlier than the second I-frame.

7. A system as recited in claim 4, wherein the act of determining whether or not to copy the first I-frame into one of the “

m”

spare buffers comprises the following;

an act of determining that the first I-frame is not to be copied into one of the “

m”

spare buffers regardless of the number of spare buffers available.

8. A system as recited in claim 1, wherein the stored MPEG stream includes a set of temporally adjacent frames in the sequence I-frame, B-frame, B-frame, P-frame, B-frame, B-frame, P-frame, B-frame, B-frame, P-frame, B-frame, B-frame, P-frame, B-frame, B-frame.

9. A system as recited in claim 1, wherein the system comprises a DVD.

10. A system as recited in claim 1, wherein the system comprises a DVB.

11. A system as recited in claim 1, wherein the system comprises a VCR.

12. A system as recited in claim 1, wherein the system comprises a DSS.

13. A computer program product for use in a system that includes an MPEG decoder and has access to a stored MPEG stream that includes I-frames, P-frames, and B-frames, the computer program product comprising one or more computer-readable media having computer-executable instructions for implementing a method for displaying the stored MPEG stream in a reverse mode without requiring simultaneous buffering of all frames between temporally adjacent I-frames, wherein the method comprises:

an act of buffering two temporally adjacent I-frames, including a first I-frame and a second I-frame that is temporally later in the stored MPEG stream;

a step for displaying video data encoded in the second I-frame, a particular reconstructed P-frame temporally adjacent to the second I-frame, and reconstructed B-frames between the second I-frame and the particular reconstructed P-frame, in reverse sequence, the particular reconstructed P-frame having been iteratively reconstructed from the first I-frame; and

an act of iteratively reconstructing other B-frames between the first I-frame and the particular reconstructed P-frame to continue displaying video data encoded in frames in the reverse sequence compared to the original sequence without simultaneously buffering all frames between the first I-frame and the second I-frame.

14. The computer program product as recited in claim 13, wherein two B-frames are reconstructed between the second I-frame and the particular reconstructed P-frame.

15. The computer program product as recited in claim 14, wherein the video data encoded in the second I-frame is displayed, then the video data encoded in the two reconstructed B-frames are displayed and then video data encoded in the particularly reconstructed P-frame is displayed.

16. A system that includes an MPEG decoder and has access to a stored MPEG stream that includes I-frames, P-frames, and B-frames, wherein the system is configured for implementing a method for displaying the stored MPEG stream in a reverse mode without requiring simultaneous buffering of all frames between temporally adjacent I-frames, the system comprising:

one or more computer-readable media having computer-executable instructions for implementing the method, wherein the method comprises;

an act of buffering two temporally adjacent I-frames, including a first I-frame and a second I-frame that is temporally later in the stored MPEG stream;

a step for displaying video data encoded in the second I-frame, a particular reconstructed P-frame temporally adjacent to the second I-frame, and reconstructed B-frames between the second I-frame and the particular reconstructed P-frame, in reverse sequence, the particular reconstructed P-frame having been iteratively reconstructed from the first I-frame; and

an act of iteratively reconstructing other B-frames between the first I-frame and the particular reconstructed P-frame to continue displaying video data encoded in frames in the reverse sequence compared to the original sequence without simultaneously buffering all frames between the first I-frame and the second I-frame.

17. The system as recited in claim 16, wherein two B-frames are reconstructed between the second I-frame and the particular reconstructed P-frame.

18. The system as recited in claim 17, wherein the video data encoded in the second I-frame is displayed, then the video data encoded in the two reconstructed B-frames are displayed and then video data encoded in the particularly reconstructed P-frame is displayed.

19. A system as recited in claim 16, wherein the system comprises at least one or more of a DVD, a DVB, a VCR or a DSS.

20. A system as recited in claim 16, wherein the system comprises a PC.