diff --git a/index.src.html b/index.src.html index b6adba8f..b871105d 100644 --- a/index.src.html +++ b/index.src.html @@ -127,6 +127,11 @@ inputs are provided. The underlying codec implementation MUST emit all outputs in response to a flush. +: Priming Samples +:: Audio samples produced at the start of decoding that represent encoder delay + or filter warm-up and are not part of the original audio content. Also + commonly referred to as "encoder delay" or "pre-skip". + : Codec System Resources :: Resources including CPU memory, GPU memory, and exclusive handles to specific decoding/encoding hardware that MAY be allocated by @@ -334,6 +339,9 @@ : [[dequeue event scheduled]] :: A boolean indicating whether a {{AudioDecoder/dequeue}} event is already scheduled to fire. Used to avoid event spam. +: [[priming samples to discard]] +:: An integer representing the number of [=priming samples=] remaining to be + discarded from decoded audio outputs. Constructors {#audiodecoder-constructors} ----------------------------------------- @@ -354,7 +362,8 @@ 11. Assign `0` to {{AudioDecoder/[[decodeQueueSize]]}}. 12. Assign a new [=list=] to {{AudioDecoder/[[pending flush promises]]}}. 13. Assign `false` to {{AudioDecoder/[[dequeue event scheduled]]}}. -13. Return d. +14. Assign `0` to {{AudioDecoder/[[priming samples to discard]]}}. +15. Return d. Attributes {#audiodecoder-attributes} ------------------------------------- @@ -407,7 +416,12 @@ 3. If needed, assign {{AudioDecoder/[[codec implementation]]}} with an implementation supporting |config|. 4. Configure {{AudioDecoder/[[codec implementation]]}} with |config|. - 5. [=queue a task=] to run the following steps: + 5. Assign {{AudioDecoder/[[priming samples to discard]]}} with the + number of [=priming samples=] indicated by + |config|.{{AudioDecoderConfig/description}}, as defined by the + codec's registration in the [[WEBCODECS-CODEC-REGISTRY]], or `0` + if not specified. + 6. [=queue a task=] to run the following steps: 1. Assign `false` to {{AudioDecoder/[[message queue blocked]]}}. 2. [=Queue a task=] to [=Process the control message queue=]. 3. Return `"processed"`. @@ -443,18 +457,21 @@ 3. Decrement {{AudioDecoder/[[decodeQueueSize]]}} and run the [=AudioDecoder/Schedule Dequeue Event=] algorithm. 4. Enqueue the following steps to the {{AudioDecoder/[[codec work queue]]}}: - 1. Attempt to use {{AudioDecoder/[[codec implementation]]}} to decode + 1. If |chunk| contains [=priming samples=] information, update + {{AudioDecoder/[[priming samples to discard]]}} as defined by the + codec's registration in the [[WEBCODECS-CODEC-REGISTRY]]. + 2. Attempt to use {{AudioDecoder/[[codec implementation]]}} to decode the chunk. - 2. If decoding results in an error, [=queue a task=] to run the + 3. If decoding results in an error, [=queue a task=] to run the [=Close AudioDecoder=] algorithm with {{EncodingError}} and return. - 3. If {{AudioDecoder/[[codec saturated]]}} equals `true` and + 4. If {{AudioDecoder/[[codec saturated]]}} equals `true` and {{AudioDecoder/[[codec implementation]]}} is no longer [=saturated=], [=queue a task=] to perform the following steps: 1. Assign `false` to {{AudioDecoder/[[codec saturated]]}}. 2. [=Process the control message queue=]. - 4. Let |decoded outputs| be a [=list=] of decoded audio data outputs + 5. Let |decoded outputs| be a [=list=] of decoded audio data outputs emitted by {{AudioDecoder/[[codec implementation]]}}. - 5. If |decoded outputs| is not empty, [=queue a task=] to run the + 6. If |decoded outputs| is not empty, [=queue a task=] to run the [=Output AudioData=] algorithm with |decoded outputs|. 5. Return `"processed"`. @@ -555,22 +572,33 @@
Run these steps: 1. For each |output| in |outputs|: - 1. Let |data| be an {{AudioData}}, initialized as follows: - 1. Assign `false` to {{platform object/[[Detached]]}}. - 2. Let |resource| be the [=media resource=] described by |output|. - 3. Let |resourceReference| be a reference to |resource|. - 4. Assign |resourceReference| to - {{AudioData/[[resource reference]]}}. - 5. Let |timestamp| be the {{EncodedAudioChunk/[[timestamp]]}} of the - {{EncodedAudioChunk}} associated with |output|. - 6. Assign |timestamp| to {{AudioData/[[timestamp]]}}. - 7. If |output| uses a recognized {{AudioSampleFormat}}, assign that - format to {{AudioData/[[format]]}}. Otherwise, assign `null` to - {{AudioData/[[format]]}}. - 8. Assign values to {{AudioData/[[sample rate]]}}, - {{AudioData/[[number of frames]]}}, and - {{AudioData/[[number of channels]]}} as determined by |output|. - 3. Invoke {{AudioDecoder/[[output callback]]}} with |data|. + 1. Let |discardedFrames| be the lesser of the number of frames of + |output| and {{AudioDecoder/[[priming samples to discard]]}}. + 2. Decrement {{AudioDecoder/[[priming samples to discard]]}} by + |discardedFrames|. + 3. Remove the first |discardedFrames| frames from |output|. + 4. If the number of frames of |output| is greater than 0: + 1. Let |data| be an {{AudioData}}, initialized as follows: + 1. Assign `false` to {{platform object/[[Detached]]}}. + 2. Let |resource| be the [=media resource=] described by |output|. + 3. Let |resourceReference| be a reference to |resource|. + 4. Assign |resourceReference| to + {{AudioData/[[resource reference]]}}. + 5. Let |timestamp| be the {{EncodedAudioChunk/[[timestamp]]}} of the + {{EncodedAudioChunk}} associated with |output|. + 6. If |discardedFrames| is greater than 0: + 1. Increment |timestamp| by the result of dividing + |discardedFrames| by the sample rate of |output|, + multiplied by 1,000,000. + 2. Round |timestamp| to the nearest integer. + 7. Assign |timestamp| to {{AudioData/[[timestamp]]}}. + 8. If |output| uses a recognized {{AudioSampleFormat}}, assign that + format to {{AudioData/[[format]]}}. Otherwise, assign `null` to + {{AudioData/[[format]]}}. + 9. Assign values to {{AudioData/[[sample rate]]}}, + {{AudioData/[[number of frames]]}}, and + {{AudioData/[[number of channels]]}} as determined by |output|. + 2. Invoke {{AudioDecoder/[[output callback]]}} with |data|.
Reset AudioDecoder (with |exception|)
@@ -587,6 +615,7 @@ 6. For each |promise| in {{AudioDecoder/[[pending flush promises]]}}: 1. [=Reject=] |promise| with |exception|. 2. Remove |promise| from {{AudioDecoder/[[pending flush promises]]}}. + 7. Set {{AudioDecoder/[[priming samples to discard]]}} to `0`.
Close AudioDecoder (with |exception|)