Signaling field type information

1. In a computing device that implements a video decoder, a method of decoding video comprising:

receiving, at the video decoder, a first code from a bit stream, wherein the first code indicates a frame coding mode of a video frame, and wherein the first code indicates that the frame coding mode for the video frame is field-coded interlaced;

receiving, at the video decoder, a second code from the bit stream for the field-coded interlaced video frame, wherein the field-coded interlaced video frame has two fields arranged in the bit stream for decoding as individual fields; and

with the video decoder, decoding the second code, wherein the second code represents information that jointly indicates two separate field types for the two fields, respectively, and an order for the two separate field types for the two fields, and wherein each of the two separate field types is capable of being any of an intra-coded field (I), a predictive-coded field (P), a bi-directionally predictive-coded field (B), and a bi-directionally predictive-coded field with only intra-coded macroblocks (BI);

wherein the decoding the second code comprises looking up the second code in a table that maps different second code values to different combinations of the two separate field types.

2. The method of claim 1 wherein the order for the two separate field types is selected from the group consisting of I/I, I/P, P/I, P/P, B/B, B/BI, BI/B, and BI/BI.

3. The method of claim 1 wherein the second code is signaled at frame layer for the interlaced video frame.

4. The method of claim 1 wherein the second code is a fixed length code.

5. The method of claim 1 wherein the frame coding mode is selected from the group consisting of: progressive, frame-coded interlaced, and field-coded interlaced.

6. The method of claim 1 wherein the first code is a variable length code.

7. The method of claim 1 wherein the first code is signaled at frame layer for the field-coded interlaced video frame.

8. The method of claim 1 wherein the computing device includes a display and a wireless communication connection, the bit stream being received over the wireless communication connection.

9. In a computing device that implements a video encoder, a method of encoding video comprising:

with the video encoder, encoding a first code for a video frame, wherein the first code indicates a frame coding mode of the video frame, and wherein the first code indicates that the frame coding mode for the video frame is field-coded interlaced;

with the video encoder, encoding a second code for the field-coded interlaced video frame, wherein the field-coded interlaced video frame has two fields arranged in a bit stream for decoding as individual fields, wherein the second code represents information that jointly indicates two separate field types for the two fields, respectively, and an order for the two separate field types for the two fields, and wherein the two separate field types are capable of having two different field types; and

with the video encoder, signaling the first code and the second code in the bit stream.

10. The method of claim 9 wherein the order for the two separate field types is selected from the group consisting of: I/I, I/P, P/I, P/P, B/B, B/BI, BI/B, and BI/BI.

11. The method of claim 9 wherein the second code is signaled at frame layer for the interlaced video frame.

12. The method of claim 9 wherein the second code is a fixed length code.

13. The method of claim 9 wherein the frame coding mode is selected from the group consisting of: progressive, frame-coded interlaced, and field-coded interlaced.

14. The method of claim 9 wherein the first code is a variable length code.

15. The method of claim 9 wherein the first code is signaled at frame layer for the interlaced video frame.

16. The method of claim 9 wherein the encoding the second code comprises looking up a combination for the two separate field types for the two fields in a table that maps different second code values to different combinations of the two separate field types.

17. The method of claim 9 wherein the computing device includes a display and a wireless communication connection, the bit stream being signaled over the wireless communication connection.

18. A system that implements a video decoder, the system comprising:

one or more processors;

memory;

at least one input device, output device or communication connection; and

one or more storage media storing instructions for causing the system to decode video using:

means for decoding a frame coding mode syntax element signaled at frame layer for a video frame, wherein the frame coding mode syntax element indicates a frame coding mode for the video frame; and

means for decoding a field picture type syntax element signaled at frame layer for the video frame when the frame coding mode is field-coded interlaced, wherein the field picture type syntax element jointly indicates two separate field types for two fields, respectively, of the video frame and a field type sequence for the two fields of the video frame, wherein the two fields of the video frame are arranged in a bit stream for decoding as individual fields, and wherein the field type sequence is capable of being any of I/I, I/P, P/I, P/P, B/B, B/BI, BI/B, and BI/BI.

19. The system of claim 18 wherein the frame coding mode syntax element is a variable length code and the field picture type syntax element is a fixed length code.

20. The system of claim 18 wherein the one or more storage media further store instructions for causing the system to decode video using:

means for decoding a picture type syntax element signaled at frame layer for the video frame when the frame coding mode is frame-coded interlaced or progressive, wherein the picture type syntax element indicates a picture type for the video frame.

21. A computing device that implements a video decoder, the computing device comprising:

one or more processors;

memory;

a display

a wireless communication connection; and

one or more storage media storing instructions for causing the computing device to perform a method of decoding video comprising:

receiving, via the wireless communication connection, a bit stream;

decoding a frame coding mode syntax element signaled at frame layer in the bit stream for a video frame, wherein the frame coding mode syntax element indicates a frame coding mode for the video frame; and

decoding a field picture type syntax element signaled at frame layer in the bit stream for the video frame when the frame coding mode is field-coded interlaced, wherein the field picture type syntax element jointly indicates two separate field types for two fields, respectively, of the video frame and a field type sequence for the two fields of the video frame, wherein the two fields of the video frame are arranged in a bit stream for decoding as individual fields, and wherein the field type sequence is capable of being any of I/I, I/P, P/I, P/P, B/B, B/BI, BI/B, and BI/BI.