[FFmpeg-devel] [PATCH 3/5] add AV_DISPOSITION_IMPAIRED for describing streams intended for hearing or visually impaired persons

Justin Ruggles justin.ruggles
Sat Feb 5 19:33:49 CET 2011

On 02/05/2011 04:40 AM, Reimar D?ffinger wrote:

> On Fri, Feb 04, 2011 at 08:53:35PM -0500, Justin Ruggles wrote:
>> On 02/04/2011 08:11 PM, Peter Ross wrote:
>>> ---
>>>  libavformat/avformat.h |    1 +
>>>  libavformat/version.h  |    2 +-
>>>  2 files changed, 2 insertions(+), 1 deletions(-)
>>> diff --git a/libavformat/avformat.h b/libavformat/avformat.h
>>> index 83289e4..160695e 100644
>>> --- a/libavformat/avformat.h
>>> +++ b/libavformat/avformat.h
>>> @@ -472,6 +472,7 @@ typedef struct AVIndexEntry {
>>>   * even when user did not explicitly ask for subtitles.
>>>   */
>>>  #define AV_DISPOSITION_FORCED    0x0040
>>> +#define AV_DISPOSITION_IMPAIRED  0x0080  /**< stream for the hearing or visually impaired */
>> I think it might be useful to have separate values for hearing and
>> visually impaired so that an application could provide an easy way for
>> users with one or the other impairment to select specific streams for
>> their needs.
> Not objecting, but which kind of stream can you imagine where it's not
> obvious?
> I mean I've never seen a video or subtitle stream for visually impaired
> nor an audio stream for the hearing-impaired...

Apparently audio streams for the hard-of-hearing do exist.

Enabling the Disabled in Digital Cinema:

"A hearing-impaired audio channel, known in the industry as HI audio, is
a monophonic mix of that which is heard in the auditorium speakers, but
with added emphasis on the dialog track."

Dolby Metadata Guide:

"Associated Service: Hearing Impaired (HI) - This is typically a
single-channel program intended to convey audio that has been processed
for increased intelligibility and decoded along with the main audio
service. The HI service may also be a complete mix of all program
channels, comprising up to six channels."


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