Comments on open issues for MPEG-4 AVC supplement 2009/04/22 JAHIS, Karl Storz

2009/04/ Outline Comments on open issues Re-encoding Aspect ratio Audio format Media profile

2009/04/ Re-encoding We do not use re-encoding in most cases. Re-encoding issue should be taken care in the system design and we do not have to take care in the MPEG-4 AVC / H.264 supplement.

2009/04/ Aspect Ratio We should standardize formats supported by the current hardware encoders/decoders in the first version of the supplement. Image size: 1920x1080, 1280x720 Chroma sampling: 4:2:0 Bit depth: 8 bits

2009/04/ Audio Format AC3 as a new format of audio codec should be defined in the MPEG-4 AVC supplement as accompanying audio with MPEG-4 AVC video. Note: MP3 format is defined as the accompanying audio with MPEG-2 video (see Appendix).

2009/04/ Media Profile The BD standard is a private (non-open) standard at present and has on-going items to be standardized. It is difficult to standardize a new media profile with MPEG-4 AVC supplement, because we cannot wait until the BD standard becomes an open standard. We are not sure if WG13 is suitable for a new media profile standardization.

2009/04/ Appendix: Audio Format DICOM standard has description related to audio in the DICOM standard as follows. 1.In sections A.32.5 (Video Endoscopic Image Information Object Definition), A.32.6 (Video Microscopic Image Information Object Definition) and A.32.7 (Video Photographic Image Information Object Definition) in PS , Image Information Object Definitions about Videos are defined. In each section, it says “The video may include audio channel(s) for acquiring patient voice or physiological sounds, healthcare professionals’ commentary, or environmental sounds” in note 3. Note: Since there is no description about audio format here, the audio format should be defined in Transfer Syntax. In the current specification, only MPEG-2 Transfer Syntax includes audio data (MP3) (see below). 2.In A.34.2 (Basic Voice Audio Information Object Definition), the basic voice audio IOD is specified as "The Basic Voice Audio IOD is the specification of a digitized sound that has been acquired or created by an audio modality or by an audio acquisition function within an imaging modality. A typical use is report dictation." Note: Audio data is explained in section C.10.9 (Waveform). Audio is defined as Waveform Data (PCM audio). PCM audio is not defined as an audio format but one of Waveform Data. 3.In (MPEG2 IMAGE COMPRESSION) in PS , it says “Any audio components present within the MPEG bit stream shall comply with the following restrictions: CBR MPEG-1 LAYER III (MP3) Audio Standard.” MP3 is defined only here in the DICOM specification. Which means that MP3 audio can be used only with MPEG-2 video.