Intra/inter mode decision for predictive frame encoding

Patent metadata

Field	Value
Publication number	US-9560350-B2
Application number	US-75121110-A
Country	US
Kind code	B2
Filing date	Mar 31, 2010
Priority date	Mar 31, 2009
Publication date	Jan 31, 2017
Grant date	Jan 31, 2017

Abstract

This invention predicts that intra mode prediction is more effective for the macro blocks where motion estimation in inter mode prediction fails. This failure is indicated by a large value of the inter mode SAD. This invention performs intra mode prediction for only macro blocks have larger inter mode SADs. The definition of a large inter mode SAD differs for different content. This invention compares the inter mode SAD of a current macroblock with an adaptive threshold. This adaptive threshold depends on the average and variance of the SADs of the previous predicted frame. An adaptive threshold is calculated for each new predictive frame.

First claim

What is claimed is:

1. A method of transforming a video into an encoded, compressed video comprising the steps of:
receiving an input video in the form of a plurality of sequential frames;
dividing each frame into a plurality of macroblocks;
for each macroblock in each frame of the video
calculating a best measure of similarity for inter mode predictive coding of the macroblock,
comparing the calculated best measure of similarity for inter mode predictive coding with a predetermined threshold,
if the calculated best measure of similarity for inter mode predictive coding is less than the predetermined threshold, then inter mode predictive coding the macroblock,
if the calculated best measure of similarity for inter mode predictive coding is not less than the predetermined threshold, then
calculating a best measure of similarity for intra mode predictive coding of the macroblock,
comparing the calculated best measure of similarity for inter mode predictive coding with the best measure of similarity for intra mode predictive coding,
if the calculated best measure of similarity for inter mode predictive coding is less than the best measure of similarity for intra mode predictive coding, then inter mode predictive coding the macroblock,
if the calculated best measure of similarity for inter mode predictive coding is not less than the predetermined threshold, then intra mode predictive coding the macroblock;

outputting an output video having the thus encoded macroblocks;
upon completion of a frame, calculating a new predetermined threshold for a next frame including
calculating an average SAD (avg_sad) over the frame as follows

avg_sad
=

1
M

⁢

∑

i
=
1

M

⁢

⁢

sad
⁡

[
i
]

where: M is a number of macroblocks in the frame; and sad[i] is the calculated inter mode SAD for the i-th macroblock,
calculating a variance in average SAD over the frame (var_sad) as follows:

var_sad
=

1
M

⁢

∑

i
=
1

M

⁢

⁢

(

sad
⁡

[
i
]

-
ave_sad

)

2

,

calculating an average SAD per pixel (avg_sad_pp) as follows:

avg_sad
⁢
_pp

=

avg_sad
N

,

calculating an average variance in SAD per pixel (var_sad_pp) as follows:

var_sad
⁢
_pp

=

var_sad

N
2

where: N is a number of pixels per macroblock, and
calculating a new value of the predetermined threshold for a next frame as follows:
FastIntraThrehold[ n ]=(1−QF*var_sad_pp[ n− 1])*avg_sad_pp[ n− 1]

where: QF is an empirical quality factor.

2. The method of claim 1 , wherein:
the quality factor is selected from a set { 0 , 1 , 2 , 3 , 4 , 5 }; and
a quality factor level 0 eliminates intra mode SAD computations for all macroblocks.

3. The method of claim 1 , wherein:
the quality factor is selected from a set { 0 , 1 , 2 , 3 , 4 , 5 }; and
a quality factor level 5 causes intra mode SAD calculation for every macroblock.

4. An apparatus transforming a video into an encoded, compressed video comprising:
a memory receiving and storing an input video in the form of a plurality of sequential frames;
a digital signal processor connected to said memory programmed to
divide each frame stored in said memory into a plurality of macroblocks;
for each macroblock in each frame of said video
calculate a best measure of similarity for inter mode predictive coding of said macroblock,
compare said calculated best measure of similarity for inter mode predictive coding with a predetermined threshold,
if said calculated best measure of similarity for inter mode predictive coding is less than the predetermined threshold, then inter mode predictive code said macroblock,
if said calculated best measure of similarity for inter mode predictive coding is not less than the predetermined threshold, then
calculate a best measure of similarity for intra mode predictive coding of said macroblock,
compare said calculated best measure of similarity for inter mode predictive coding with the best measure of similarity for intra mode predictive coding,
if said calculated best measure of similarity for inter mode predictive coding is less than said best measure of similarity for intra mode predictive coding, then inter mode predictive code the macroblock,
if said calculated best measure of similarity for inter mode predictive coding is not less than said predetermined threshold, then intra mode predictive code the macroblock;

output an output video having the thus encoded macroblocks;

said digital signal processor is further programmed to calculate a new predetermined threshold for a next frame upon completion of said frame including
calculate an average SAD (avg_sad) over said frame as follows

avg_sad
=

1
M

⁢

∑

i
=
1

M

⁢

⁢

Assignees

• Nagori Soyeb
• Mathew Manu
• Swami Pramod Kumar
• Texas Instruments Inc

Inventors

• Nagori Soyeb
• Mathew Manu
• Swami Pramod Kumar

Classifications

• H04N19/176

  the region being a block, e.g. a macroblock · CPC title

• H04N19/147

  according to rate distortion criteria (rate-distortion as a criterion for motion estimation H04N19/567) · CPC title

• H04N19/107 Primary

  between spatial and temporal predictive coding, e.g. picture refresh · CPC title

• H04N19/00569 Primary

  Electricity · mapped topic

• H04N19/50

  using predictive coding (H04N19/61 takes precedence) · CPC title