Re: Using WebVTT metadata tracks and missing API

Hi Cyril,

On Mon, Nov 11, 2013 at 5:49 PM, Cyril Concolato
<cyril.concolato@telecom-paristech.fr> wrote:
>
> Le 30/10/2013 10:03, Silvia Pfeiffer a écrit :
>
>> BTW: We need to keep the connection between the video and the VTT
>> resource to a minimum - in particular I object to adding the mime type
>> of the media resource, or the codec, or codec paramters to the vtt
>> file header. The VTT file needs to be able to be used with different
>> encodings of the same video file through the <track> element, which
>> can relate to different <source> elements.
>>
>> So, the following header fields that you are using are actually
>> harmful: baseMediaFile, MPEG-4-streamType,
>> MPEG-4-objectTypeIndication, sampleRate, numChannels,
>> MPEG-4-DecoderSpecificInfo . Please don't start exposing such
>> information in a VTT file. This information must not be made part of a
>> VTT file - it is far too easy to get out of sync with an actual video
>> file and is already out of sync with a different encoding of the same
>> video file. The VTT file is not a companion file to a specific media
>> resource. If you need to expose such information in a file, I
>> recommend writing a separate file, e.g. video_metadata.xml.
>
> You misunderstood me. The information is not duplicated in the VTT file, it
> is *only* in the VTT file. In this example, I assume that some
> audio/video/other data carried in some original media container (say mp4) is
> not supported but the browser's demultiplexing stack and thus not exposed to
> JS API via a VideoTrack or AudioTrack interface. So to work around that
> limitation, I'm thinking about using WebVTT to expose the data (or a
> reference to the data). In the example, I'm putting the information that was
> initially in the MP4 file in the WebVTT file: some in the header (from MP4
> header to VTT header), some in the cue data (from MP4 samples to VTT cues).

What is a JS developer supposed to do with this information?

Silvia.

Received on Monday, 11 November 2013 10:06:48 UTC