International organisation for standardisation

6.10.2Supplemental information

6.10.2.1.1.1.1.1.1JCTVC-F289 On VUI syntax parameters [M. Haque, A. Tabatabai, T. Suzuki (Sony)]

This document discusses the VUI parameters defined in AVC. The AVC VUI syntax structures are shown in a tabular form with some remarks about their possible usage in HEVC context.

The contribution basically advocates reuse of all AVC VUI except any relating to field coding (e.g., pic_struct_present_flag). It was agreed that relative chroma grid positioning should be included (not field-specific). max_bits_per_mb_denom needs further study – we plan to leave that out for now.

Decision: Agreed (adjusted as described above, as a starting point).

Should also investigate SVC related VUI to identify any additional needs.

6.10.2.1.1.1.1.1.2JCTVC-F291 Picture Orientation Information [D. Hong, J. Boyce, S. Wenger (Vidyo)]

This contribution proposes to include in the bitstream the picture orientation information of each coded picture. This contribution follows on the prior JCTVC-E280 and provides the flexibility to change picture orientation on a picture level, even for non-IDR pictures. Some video capturing devices capture pictures in an orientation different from the orientation needed for rendering and the encoding side can save the compute needed to properly rotate the pictures by signalling the picture orientation information to the decoding end, and thus, deferring the rotation process to the rendering module; for rendering, many systems use hardware GPUs that also support picture rotation. Additionally, a picture may be coded in a certain orientation for improved coding efficiency. In the low-complexity setting, utilizing the ability to change picture orientation between 0 and 90 degrees, the contribution reports (0.6%, 0.9%, 1.1%), (0.6%, 0.4%, 0.8%), and (0.1%, 0.2%, 0.4%) (Y, Cb, Cr) BD-rate gain for intra only, random access, and low delay, respectively. Individual sequence BD-rate gains for the low-complexity setting were reportedly as high as (3.4%, 3.2%, 4.4%), (2.8%, 2.1%, 3.9%), and (0.3%, 2.1%, 2.5%) for intra only, random access, and low delay, respectively.

Not just display hint information, but also as a coding tool.

Which sequence gave 3.4%? Answer: Traffic.

Fast method provided almost the same amount of gain.

Proposes to change the motion compensation process and temporal MV prediction process in response to changes in the indicated rotation.

A display hint SEI (as in JCTVC-E380) seems easier to justify than the normative decoding process modification.

Some prior notes from review of JCTVC-E280:

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  It was noted that this is not really a proposed "decoder processing" scheme, but rather some "display helper information".
  
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  It was remarked that some similar issues were discussed previously in JCTVC-C224.
  
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  It was remarked that performing an image rotation at the encoder side could also add delay.
  
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  It was remarked that the orientation information is a property of the video, which could mean that it is advantageous to convey the information in a tightly-coupled fashion with the video bitstream.
  
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  It was remarked that having this information at both the video and system layer could occur, and there would need to be some prioritization in the event of multiple indicators.
  
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  It was remarked that such a concept is not specific to HEVC, and could be considered for AVC as well.
  
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  It was remarked that doing it in SEI would allow the indicator to change dynamically, and that angles other than 90 degree increments should perhaps be considered, as the display process can choose to quantize that to 90 degree increments if it so chooses. Other more elaborate possibilities were also discussed.
  

It was remarked that a flip bit may also be beneficial to add in such an SEI message.

We are favorably inclined to add an SEI message such as this, but it is not our priority at the moment.

Let's defer such consideration of new SEI messages (not per JCTVC-E346) for a couple of meeting cycles.