Multi-rate processing for image data in an image processing pipeline

1. An apparatus, comprising:

an image signal processor that comprises:

one or more front-end pipeline stages that processes pixels at an initial rate of pixels per clock cycle;

a scaler; and

one or more back-end pipeline stages that processes pixels at a different rate of pixels per clock cycle that is less than the initial rate of pixels per clock cycle, wherein the one or more back-end pipeline stages process the pixels subsequent to the one or more front-end pipeline stages;

the image signal processor, configured to:

receive a stream of pixel data collected at an image sensor according to an initial data size for an image frame;

process the stream of pixel data through the one or more front-end pipeline stages of the image signal processor;

scale, by the scaler, the stream of pixel data to a data size that is less than the initial data size for the stream of pixel data;

process the stream of scaled pixel data through the one or more back-end pipeline stages; and

provide the stream of scaled pixel data processed through the one or more back-end pipeline stages for display of the image frame.

2. The apparatus of claim 1 , wherein the image signal processor is further configured to write the stream of pixel data processed through the one or more front-end pipeline stages to a memory such that the image frame is written to the memory according to the initial data size.

3. The apparatus of claim 1 ,

wherein the image signal processor further comprises a demosaic unit;

wherein the stream of pixel data collected at the image sensor is raw pixel data;

wherein the image signal processor is further configured to:

convert, by the demosaic unit the stream of pixel data processed through the one or more front-end pipeline stages into a full-color domain, wherein the converted stream of pixel data comprises a luminance component and one or more chrominance components; and

resample, by the scaler, the converted stream of pixel data to reduce the one or more chrominance components without reducing the luminance component; and

write the resampled stream of pixel data to a memory.

4. The apparatus of claim 3 , wherein the image signal processor is further configured to:

access the memory to obtain the resampled stream of pixel data;

convert the resampled stream of pixel data to increase the one or more chrominance components; and

process the resampled stream of pixel data with the increased one or more chrominance components through the one or more back-end pipeline stages.

5. The apparatus of claim 1 ,

wherein the image signal processor further comprises an image processing interface for the one or more back-end pipeline stages, wherein the one or more back-end pipeline stages process pixels according to a particular color format;

wherein the image signal processor is further configured to:

receive a stream of other pixel data via the image processing interface in a color format different than the particular color format;

convert, by the image processing interface, the stream of other pixel data to the particular color format; and

process the stream of other pixel data converted to the particular format through the one or more back-end pipeline stages.

6. The apparatus of claim 5 , wherein the apparatus comprises the image sensor and wherein the stream of other pixel data is not collected at the image sensor.

7. The apparatus of claim 1 , wherein the apparatus comprises a mobile computing device.

8. A method, comprising:

receiving, at an image signal processor, a stream of raw pixel data collected for an image frame according to an initial data size;

directing the stream of raw pixel data through one or more pipeline stages of the image signal processor that process pixels at an initial rate of pixels per clock cycle;

converting, by the image signal processor, the stream of raw pixel data into a full-color domain;

scaling, by the image signal processor, the stream of converted pixel data to a different data size that is less than the initial data size; and

directing the stream of scaled pixel data through one or more other pipeline stages at the image signal processor that process pixels at a different rate of pixels per clock cycle, wherein the different rate of pixels per clock cycle is less than the initial rate of pixels per clock cycle.

9. The method of claim 8 , further comprising storing, by the image signal processor, the stream of raw pixel data processed through the one or more pipeline stages to a memory.

10. The method of claim 8 , further comprising storing, by the image signal processor, the stream of converted pixel data to a memory.

11. The method of claim 10 , wherein the converted stream of pixel data comprises a luminance component and one or more chrominance components, and wherein storing the stream of converted pixel data comprises resampling the converted stream of pixel data to reduce the one or more chrominance components without reducing the luminance component.

12. The method of claim 10 , further comprising:

storing the stream of scaled pixel data processed through the one or more other pipeline stages as a part of a collection image frames in a video recording;

receiving, from the memory, the stream of converted pixel data;

directing the stream of converted pixel data through the one or more other pipeline stages; and

storing the stream of converted pixel data processed through the one or more other pipeline stages as a version of the image frame with a higher image resolution than the video recording.

13. The method of claim 8 , wherein the one or more pipeline stages are front-end pipeline stages, wherein the one or more other pipeline stages are back-end pipeline stages, and wherein the method further comprises:

receiving, via an interface at the image signal processor for the back-end pipeline stages, a stream of other pixel data; and

processing the stream of other pixel data through the one or more back-end pipeline stages.

14. The method of claim 13 , wherein the image signal processor is implemented as part of a mobile computing device, and wherein the stream of other pixel data is received at the mobile computing device over a network from a remote server.

15. A system, comprising:

a device configured to perform image processing, the device comprising:

a sensor interface configured to receive image data from an image sensor; and

an image processing pipeline configured to:

receive, via the sensor interface, a stream of pixel data collected from an image sensor, wherein the image sensor collects the stream of pixel data for an image frame according to an initial data size;

process the stream of pixel data through one or more raw format pipeline stages of the image signal processor that process pixels at an initial rate of pixels per clock cycle;

scale the stream of pixel data to a different data size that is less than the initial data size;

process the stream of scaled pixel data through one or more full-color pipeline stages that process pixels at a different rate of pixels per clock cycle, wherein the different rate of pixels per clock cycle is less than the initial rate of pixels per clock cycle; and

output the stream of scaled pixel data processed through the full-color pipeline stages.

16. The system of claim 15 , wherein the image processing pipeline is further configured to write the stream of pixel data processed through the one or more raw pipeline stages to a memory.

17. The system of claim 16 , wherein the image processing pipeline is further configured to:

receive from the memory the stream of pixel data; and

process the stream of pixel data through the full-color pipeline stages.

18. The system of claim 15 ,

wherein the system further comprises an interface configured to receive image data for processing through the one or more full-color pipeline stages of the image processing pipeline;

wherein the image processing pipeline is further configured to:

receive a stream of other pixel data via the interface from a different source than the image sensor; and

process the stream of other pixel data through the one or more full-color pipeline stages.

19. The system of claim 15 , wherein the system is a mobile computing device, and wherein the device is an image signal processor.

20. The system of claim 19 , wherein the mobile computing device comprises the image sensor and a display device, wherein the stream of scaled pixel data processed through the one or more full-color pipeline stages is output for display as a preview of the image frame at the display device.