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design: framestep: formatting and markup fixes
- Drop manual padding of figures - Add missing markup - Make subsections over the use cases and trim their heading not to be redundant - Minor grammar fixes
This commit is contained in:
Reynaldo H. Verdejo Pinochet
parent
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commit
8ee70333cf
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@ -32,16 +32,15 @@ short segments of data in PLAYING.
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## Use Cases
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* frame stepping in video only pipeline in PAUSED
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### video only pipeline in PAUSED
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```
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.-----. .-------. .------. .-------.
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| src | | demux | .-----. | vdec | | vsink |
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| src->sink src1->|queue|->sink src->sink |
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'-----' '-------' '-----' '------' '-------'
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``````
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.-----. .-------. .------. .-------.
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| src | | demux | .-----. | vdec | | vsink |
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| src->sink src1->|queue|->sink src->sink |
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'-----' '-------' '-----' '------' '-------'
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```
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*
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- app sets the pipeline to PAUSED to block on the preroll picture
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- app seeks to required position in the stream. This can be done
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@ -55,20 +54,19 @@ short segments of data in PLAYING.
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- sink posts `STEP_DONE` with amount of frames stepped and
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corresponding time interval.
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* frame stepping in audio/video pipeline in PAUSED
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### audio/video pipeline in PAUSED
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```
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.-----. .-------. .------. .-------.
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| src | | demux | .-----. | vdec | | vsink |
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| src->sink src1->|queue|->sink src->sink |
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'-----' | | '-----' '------' '-------'
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| | .------. .-------.
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| | .-----. | adec | | asink |
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| src2->|queue|->sink src->sink |
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'-------' '-----' '------' '-------'
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.-----. .-------. .------. .-------.
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| src | | demux | .-----. | vdec | | vsink |
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| src->sink src1->|queue|->sink src->sink |
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'-----' | | '-----' '------' '-------'
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| | .------. .-------.
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| | .-----. | adec | | asink |
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| src2->|queue|->sink src->sink |
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'-------' '-----' '------' '-------'
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```
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*
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- app sets the pipeline to PAUSED to block on the preroll picture
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- app seeks to required position in the stream. This can be done
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@ -88,7 +86,7 @@ short segments of data in PLAYING.
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there needs to be enough queueing in the pipeline to compensate
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for the accumulated audio.
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- frame stepping in audio/video pipeline in PLAYING
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### audio/video pipeline in PLAYING
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- app sets the pipeline to PAUSED to block on the preroll picture
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@ -116,23 +114,22 @@ short segments of data in PLAYING.
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A new `GST_EVENT_STEP` event is introduced to start the step operation.
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The step event is created with the following fields in the structure:
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* **`format`** GST_TYPE_FORMAT: The format of the step units
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* **`format`** `GST_TYPE_FORMAT`: The format of the step units
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* **`amount`** G_TYPE_UINT64: The amount of units to step. A 0 amount
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* **`amount`** `G_TYPE_UINT64`: The amount of units to step. A 0 amount
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immediately completes and can be used to cancel the current step and resume
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normal non-stepping behaviour to the end of the segment. A -1 amount steps
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until the end of the segment.
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* **`rate`** G_TYPE_DOUBLE: The rate at which the frames should be stepped in
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* **`rate`** `G_TYPE_DOUBLE`: The rate at which the frames should be stepped in
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PLAYING mode. 1.0 is the normal playback speed and direction of the segment,
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2.0 is double speed. A speed of 0.0 is not allowed. When performing a flushing
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step, the speed is not relevant. Note that we don't allow negative rates here,
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use a seek with a negative rate first to reverse the playback direction.
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* **`flush`** G_TYPE_BOOLEAN: when flushing is TRUE, the step is performed
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* **`flush`** `G_TYPE_BOOLEAN`: when flushing is TRUE, the step is performed
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immediately:
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*
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- In the PAUSED state the pipeline loses the PAUSED state, the
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requested amount of data is skipped and the pipeline prerolls again
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when a non-intermediate step completes. When the pipeline was
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@ -156,14 +153,14 @@ immediately:
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operation, the step operation will be performed from the position of
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the last PAUSED state.
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* **`intermediate`** G_TYPE_BOOLEAN: Signal that this step operation is an
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* **`intermediate`** `G_TYPE_BOOLEAN`: Signal that this step operation is an
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intermediate step, part of a series of step operations. It is mostly
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interesting for stepping in the PAUSED state because the sink will only perform
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a preroll after a non-intermediate step operation completes. Intermediate steps
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are useful to flush out data from other sinks in order to not cause excessive
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queueing. In the PLAYING state the intermediate flag has no visual effect. In
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all states, the intermediate flag is passed to the corresponding
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GST_MESSAGE_STEP_DONE.
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`GST_MESSAGE_STEP_DONE`.
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The application will create a STEP event to start or stop the stepping
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operation. Both stepping in PAUSED and PLAYING can be performed by means
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@ -191,15 +188,15 @@ fields.
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* **`active`**: If the step was queued or activated.
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* **`format`** GST_TYPE_FORMAT: The format of the step units that queued/activated.
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* **`format`** `GST_TYPE_FORMAT`: The format of the step units that queued/activated.
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* **`amount`** G_TYPE_UINT64: The amount of units that were queued/activated.
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* **`amount`** `G_TYPE_UINT64`: The amount of units that were queued/activated.
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* **`rate`** G_TYPE_DOUBLE: The rate and direction at which the frames were queued/activated.
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* **`rate`** `G_TYPE_DOUBLE`: The rate and direction at which the frames were queued/activated.
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* **`flush`** G_TYPE_BOOLEAN: If the queued/activated frames will be flushed.
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* **`flush`** `G_TYPE_BOOLEAN`: If the queued/activated frames will be flushed.
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* **`intermediate`** G_TYPE_BOOLEAN: If this is an intermediate step operation
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* **`intermediate`** `G_TYPE_BOOLEAN`: If this is an intermediate step operation
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that queued/activated.
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The `STEP_START` message is emitted 2 times:
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@ -218,13 +215,13 @@ possible moment.
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A new `GST_MESSAGE_STEP_DONE` message is created. It contains the
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following fields:
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* **`format`** GST_TYPE_FORMAT: The format of the step units that completed.
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* **`amount`** G_TYPE_UINT64: The amount of units that were stepped.
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* **`rate`** G_TYPE_DOUBLE: The rate and direction at which the frames were stepped.
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* **`flush`** G_TYPE_BOOLEAN: If the stepped frames were flushed.
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* **`intermediate`** G_TYPE_BOOLEAN: If this is an intermediate step operation that completed.
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* **`duration`** G_TYPE_UINT64: The total duration of the stepped units in `GST_FORMAT_TIME`.
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* **`eos`** G_TYPE_BOOLEAN: The step ended because of EOS.
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* **`format`** `GST_TYPE_FORMAT`: The format of the step units that completed.
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* **`amount`** `G_TYPE_UINT64`: The amount of units that were stepped.
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* **`rate`** `G_TYPE_DOUBLE`: The rate and direction at which the frames were stepped.
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* **`flush`** `G_TYPE_BOOLEAN`: If the stepped frames were flushed.
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* **`intermediate`** `G_TYPE_BOOLEAN`: If this is an intermediate step operation that completed.
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* **`duration`** `G_TYPE_UINT64`: The total duration of the stepped units in `GST_FORMAT_TIME`.
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* **`eos`** `G_TYPE_BOOLEAN`: The step ended because of EOS.
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The message is emitted by the element that performs the step operation.
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The purpose is to return the duration in `GST_FORMAT_TIME` of the
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