Video camera with rate control video compression
Embodiments provide a video camera that can be configured to compress video data in a manner that achieves a targeted output size in a computationally efficient manner. The video compression systems and methods can be used with DCT-based compression standards to include a rate control aspect. The rate controlled video compression methods can be configured to compress video data in real time and/or using a single pass. During compression of video data, the video compression systems and methods can modify compression parameters to achieve a targeted file size while maintaining relatively high visual quality of the compressed images.
1. An electronic device configured to compress a plurality of video frames, the electronic device comprising:
an image sensor configured to convert light incident on the image sensor into video data, the video data having a frame rate and comprising a plurality of video frames including a first video frame and a second video frame; and
one or more hardware processors programmed to:
compress a first portion of the first video frame using a first compression parameter to obtain a first compressed portion,
modify the first compression parameter based at least on a comparison of a size of the first compressed portion to an expected size of the first compressed portion to obtain a second compression parameter,
store to a memory device a value corresponding to the comparison of the size of the first compressed portion and the expected size of the first compressed portion,
compress a second portion of the first video frame using the second compression parameter to obtain a second compressed portion,
output the first compressed portion and the second compressed portion for storage to the memory device, and
compress a first portion of the second video frame using a modified first compression parameter for the second video frame, the modified first compression parameter for the second video frame being obtained based at least on the stored value corresponding to the comparison of the size of the first compressed portion and the expected size of the first compressed portion.
2. The electronic device of claim 1 , wherein the one or more hardware processors is further programmed to:
modify the first compression parameter based at least on a total size of the first compressed portion and the second compressed portion to obtain a third compression parameter,
compress a third portion of the first video frame using the third compression parameter to obtain a third compressed portion, and
store the third compressed portion to the memory device.
3. The electronic device of claim 1 , wherein the modification of the first compression parameter by the one or more hardware processors based at least on the size of the first compressed portion includes a comparison of the size of the first compressed portion to a set percentage of a maximum compressed size of the first video frame.
4. The electronic device of claim 1 , wherein the one or more hardware processors is programmed to compress the first portion a single time rather than a plurality of times.
5. The electronic device of claim 1 , wherein the first portion comprises a first plurality of slices and the second portion comprises a second plurality of slices, and the one or more hardware processors is further programmed to:
calculate a total frame size of a first compressed video frame after compressing the first video frame;
determine a size feedback value based on a targeted frame size and the total frame size of the first compressed video frame; and
modify an entropy index for the first plurality of slices and the second plurality of slices using the size feedback value, the entropy index corresponding to an amount of information in bits of the slices.
6. The electronic device of claim 1 , wherein the first portion comprises a first set of pixel values that extend across an entirety of the first video frame, and the second portion comprises a second set of pixel values that extend across the entirety of the first video frame.
7. The electronic device of claim 1 , wherein the one or more hardware processors is programmed to compress the first portion of the first video frame using a discrete cosine transform and the first compression parameter to obtain the first compressed portion, and to compress the second portion of the first video frame using the discrete cosine transformation and the second compression parameter to obtain the second compressed portion.
8. The electronic device of claim 1 , wherein the second portion is contiguous to the first portion.
9. The electronic device of claim 1 , wherein the first and second video frames are contiguous to one another.
10. An electronic device configured to compress a plurality of video frames, the electronic device comprising:
an image sensor configured to convert light incident on the image sensor into video data, the video data having a frame rate and comprising a plurality of video frames including a first video frame and a second video frame; and
one or more hardware processors programmed to:
compress a first portion of the first video frame using a first compression parameter to obtain a first compressed portion,
modify the first compression parameter based at least on a size of the first compressed portion to obtain a second compression parameter,
compress a second portion of the first video frame using the second compression parameter to obtain a second compressed portion, and
output the first compressed portion and the second compressed portion for storage to a memory device, and
wherein the modification of the first compression parameter by the one or more hardware processors based at least on the size of the first compressed portion includes a comparison of the size of the first compressed portion to an expected size of the first compressed portion, and the one or more hardware processors is further programmed to:
calculate a ratio of the size of the first compressed portion and the expected size of the first compressed portion;
store the ratio of the size of the first compressed portion and the expected size of the first compressed portion to the memory device; and
compress a first portion of the second video frame using a modified first compression parameter, the modified first compression parameter being obtained based at least on the ratio of the size of the first compressed portion and the expected size of the first compressed portion of the first video frame.
11. The electronic device of claim 10 , wherein the first and second video frames are contiguous to one another.
12. A method of compressing a plurality of video frames, the method comprising:
converting light incident on an image sensor into video data, the video data having a frame rate and comprising a plurality of video frames including a first video frame and a second video frame;
compressing a first portion of the first video frame using a first compression parameter to obtain a first compressed portion;
modifying the first compression parameter based at least on a comparison of a size of the first compressed portion to an expected size of the first compressed portion to obtain a second compression parameter;
storing to a memory device a value corresponding to the comparison of the size of the first compressed portion and the expected size of the first compressed portion;
compressing a second portion of the first video frame using the second compression parameter to obtain a second compressed portion;
outputting the first compressed portion and the second compressed portion for storage to the memory device; and
compressing a first portion of the second video frame using a modified first compression parameter for the second video frame, the modified first compression parameter for the second video frame being obtained based at least on the stored value corresponding to the comparison of the size of the first compressed portion and the expected size of the first compressed portion of the first video frame.
13. The method of claim 12 , further comprising:
modifying the first compression parameter based at least on a comparison of a total size of the first compressed portion and the second compressed portion to obtain a third compression parameter,
compressing a third portion of the first video frame using the third compression parameter to obtain a third compressed portion, and
storing the third compressed portion to the memory device.
14. The method of claim 12 , wherein said modifying the first compression parameter based at least on the size of the first compressed portion comprises comparing the size of the first compressed portion to a set percentage of a maximum compressed size of the first video frame.
15. The method of claim 12 , wherein the first portion is compressed a single time rather than a plurality of times.
16. The method of claim 12 , wherein the first portion comprises a first set of pixel values that extend across an entirety of the first video frame, and the second portion comprises a second set of pixel values that extend across the entirety of the first video frame.
17. The method of claim 12 , wherein said compressing the first portion of the first video frame comprises using a discrete cosine transform and the first compression parameter to obtain the first compressed portion, and wherein compressing the second portion of the first video frame comprises using the discrete cosine transformation and the second compression parameter to obtain the second compressed portion.
18. The method of claim 12 , wherein the second portion is contiguous to the first portion.
19. The method of claim 12 , wherein the first and second video frames are contiguous to one another.
20. A method of compressing a plurality of video frames, the method comprising:
converting light incident on an image sensor into video data, the video data having a frame rate and comprising a plurality of video frames including a first video frame and a second video frame;
compressing a first portion of the first video frame using a first compression parameter to obtain a first compressed portion;
modifying the first compression parameter based at least on a size of the first compressed portion to obtain a second compression parameter;
compressing a second portion of the first video frame using the second compression parameter to obtain a second compressed portion; and
outputting the first compressed portion and the second compressed portion for storage to a memory device, and
wherein said modifying the first compression parameter based at least on the size of the first compressed portion comprises comparing the size of the first compressed portion to an expected size of the first compressed portion, and the method further comprises:
calculating a ratio of the size of the first compressed portion and the expected size of the first compressed portion;
storing the ratio of the size of the first compressed portion and the expected size of the first compressed portion to the memory device;
compressing a first portion of the second video frame using a modified first compression parameter, the modified first compression parameter being obtained based at least on the ratio of the size of the first compressed portion and the expected size of the first compressed portion of the first video frame.
21. The method of claim 20 , wherein the first and second video frames are contiguous to one another.