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Define presentation timestamp and duration in WebCodecs spec #6

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51 changes: 29 additions & 22 deletions index.src.html
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Original file line number Diff line number Diff line change
Expand Up @@ -115,6 +115,17 @@
:: Refers generically to an instance of {{AudioDecoder}}, {{AudioEncoder}},
{{VideoDecoder}}, or {{VideoEncoder}}.

: <dfn lt="presentation timestamp|timestamp">presentation timestamp</dfn>
:: The presentation timestamp (PTS) of a media sample, which determines its
relative ordering and timing for rendering and processing. It is expressed
in microseconds. The specific epoch (e.g., zero-based from the start of a
capture, or matching a system clock) is not defined by this specification,
but timestamps <em class="rfc2119">SHOULD</em> be consistent within a single
stream.

: <dfn>presentation duration</dfn>
:: The duration of a media sample, expressed in microseconds.

: <dfn lt="Key Chunk|Key Frame">Key Chunk</dfn>
:: An encoded chunk that does not depend on any other frames for decoding. Also
commonly referred to as a "key frame".
Expand Down Expand Up @@ -2579,9 +2590,9 @@
: <dfn attribute for=EncodedAudioChunk>\[[type]]</dfn>
:: Describes whether the chunk is a [=key chunk=].
: <dfn attribute for=EncodedAudioChunk>\[[timestamp]]</dfn>
:: The presentation timestamp, given in microseconds.
:: The [=presentation timestamp=] of this {{EncodedAudioChunk}}.
: <dfn attribute for=EncodedAudioChunk>\[[duration]]</dfn>
:: The presentation duration, given in microseconds.
:: The [=presentation duration=] of this {{EncodedAudioChunk}}.
: <dfn attribute for=EncodedAudioChunk>[[byte length]]</dfn>
:: The byte length of {{EncodedAudioChunk/[[internal data]]}}.

Expand Down Expand Up @@ -2618,10 +2629,10 @@
:: Returns the value of {{EncodedAudioChunk/[[type]]}}.

: <dfn attribute for=EncodedAudioChunk>timestamp</dfn>
:: Returns the value of {{EncodedAudioChunk/[[timestamp]]}}.
:: Returns the [=presentation timestamp=] of this {{EncodedAudioChunk}}.

: <dfn attribute for=EncodedAudioChunk>duration</dfn>
:: Returns the value of {{EncodedAudioChunk/[[duration]]}}.
:: Returns the [=presentation duration=] of this {{EncodedAudioChunk}}.

: <dfn attribute for=EncodedAudioChunk>byteLength</dfn>
:: Returns the value of {{EncodedAudioChunk/[[byte length]]}}.
Expand Down Expand Up @@ -2685,9 +2696,9 @@
: <dfn attribute for=EncodedVideoChunk>\[[type]]</dfn>
:: The {{EncodedVideoChunkType}} of this {{EncodedVideoChunk}};
: <dfn attribute for=EncodedVideoChunk>\[[timestamp]]</dfn>
:: The presentation timestamp, given in microseconds.
:: The [=presentation timestamp=] of this {{EncodedVideoChunk}}.
: <dfn attribute for=EncodedVideoChunk>\[[duration]]</dfn>
:: The presentation duration, given in microseconds.
:: The [=presentation duration=] of this {{EncodedVideoChunk}}.
: <dfn attribute for=EncodedVideoChunk>[[byte length]]</dfn>
:: The byte length of {{EncodedVideoChunk/[[internal data]]}}.

Expand Down Expand Up @@ -2725,10 +2736,10 @@
:: Returns the value of {{EncodedVideoChunk/[[type]]}}.

: <dfn attribute for=EncodedVideoChunk>timestamp</dfn>
:: Returns the value of {{EncodedVideoChunk/[[timestamp]]}}.
:: Returns the [=presentation timestamp=] of this {{EncodedVideoChunk}}.

: <dfn attribute for=EncodedVideoChunk>duration</dfn>
:: Returns the value of {{EncodedVideoChunk/[[duration]]}}.
:: Returns the [=presentation duration=] of this {{EncodedVideoChunk}}.

: <dfn attribute for=EncodedVideoChunk>byteLength</dfn>
:: Returns the value of {{EncodedVideoChunk/[[byte length]]}}.
Expand Down Expand Up @@ -2879,7 +2890,7 @@
:: The number of audio channels for this {{AudioData}}.

: <dfn attribute for=AudioData>\[[timestamp]]</dfn>
:: The presentation timestamp, in microseconds, for this {{AudioData}}.
:: The [=presentation timestamp=] of this {{AudioData}}.

### Constructors ###{#audiodata-constructors}
<dfn constructor for=AudioData title="AudioData(init)">
Expand Down Expand Up @@ -2947,13 +2958,13 @@
{{AudioData/[[number of channels]]}}.

: <dfn attribute for=AudioData>timestamp</dfn>
:: The presentation timestamp, in microseconds, for this {{AudioData}}.
:: Returns the [=presentation timestamp=] of this {{AudioData}}.

The {{AudioData/numberOfChannels}} getter steps are to return
The {{AudioData/timestamp}} getter steps are to return
{{AudioData/[[timestamp]]}}.

: <dfn attribute for=AudioData>duration</dfn>
:: The duration, in microseconds, for this {{AudioData}}.
:: Returns the [=presentation duration=] of this {{AudioData}}.

The {{AudioData/duration}} getter steps are to:
1. Let |microsecondsPerSecond| be `1,000,000`.
Expand Down Expand Up @@ -3490,12 +3501,10 @@
adjustments.

: <dfn attribute for=VideoFrame>\[[duration]]</dfn>
:: The presentation duration, given in microseconds. The duration is copied
from the {{EncodedVideoChunk}} corresponding to this {{VideoFrame}}.
:: The [=presentation duration=] of this {{VideoFrame}}.

: <dfn attribute for=VideoFrame>\[[timestamp]]</dfn>
:: The presentation timestamp, given in microseconds. The timestamp is copied
from the {{EncodedVideoChunk}} corresponding to this {{VideoFrame}}.
:: The [=presentation timestamp=] of this {{VideoFrame}}.

: <dfn attribute for=VideoFrame>[[color space]]</dfn>
:: The {{VideoColorSpace}} associated with this frame.
Expand Down Expand Up @@ -3782,17 +3791,13 @@
{{VideoFrame/[[display height]]}}.

: <dfn attribute for=VideoFrame>timestamp</dfn>
:: The presentation timestamp, given in microseconds. For decode,
timestamp is copied from the {{EncodedVideoChunk}} corresponding
to this {{VideoFrame}}. For encode, timestamp is copied to the
{{EncodedVideoChunk}}s corresponding to this {{VideoFrame}}.
:: Returns the [=presentation timestamp=] of this {{VideoFrame}}.

The {{VideoFrame/timestamp}} getter steps are to return
{{VideoFrame/[[timestamp]]}}.

: <dfn attribute for=VideoFrame>duration</dfn>
:: The presentation duration, given in microseconds. The duration is copied
from the {{EncodedVideoChunk}} corresponding to this VideoFrame.
:: Returns the [=presentation duration=] of this {{VideoFrame}}.

The {{VideoFrame/duration}} getter steps are to return
{{VideoFrame/[[duration]]}}.
Expand Down Expand Up @@ -6261,6 +6266,7 @@
conditions, such as allowing a site to mutate a codec input or output while
the underlying codec is still operating on that data. This concern is mitigated
by ensuring that input and output interfaces are immutable.
</div>

Privacy Considerations{#privacy-considerations}
===============================================
Expand Down Expand Up @@ -6308,6 +6314,7 @@
budget", which depletes as authors use WebCodecs and other identifying APIs.
Upon exhaustion of the privacy budget, codec capabilities could be reduced to a
common baseline or prompt for user approval.
</div>

Best Practices for Authors Using WebCodecs{#best-practices-developers}
======================================================================
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