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design: framestep: formatting and markup fixes

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- 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 2016-12-21 23:09:41 -08:00
parent 8c0afd11c2
commit 8ee70333cf
1 changed files with 34 additions and 37 deletions
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markdown/design/framestep.md
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@ -32,16 +32,15 @@ short segments of data in PLAYING.
## Use Cases ## Use Cases
* frame stepping in video only pipeline in PAUSED ### video only pipeline in PAUSED
``` ```
.-----. .-------. .------. .-------. .-----. .-------. .------. .-------.
| src | | demux | .-----. | vdec | | vsink | | src | | demux | .-----. | vdec | | vsink |
| src->sink src1->|queue|->sink src->sink | | src->sink src1->|queue|->sink src->sink |
'-----' '-------' '-----' '------' '-------' '-----' '-------' '-----' '------' '-------'
`````` ```
*
- app sets the pipeline to PAUSED to block on the preroll picture - app sets the pipeline to PAUSED to block on the preroll picture
- app seeks to required position in the stream. This can be done - app seeks to required position in the stream. This can be done
@ -55,20 +54,19 @@ short segments of data in PLAYING.
- sink posts `STEP_DONE` with amount of frames stepped and - sink posts `STEP_DONE` with amount of frames stepped and
corresponding time interval. corresponding time interval.
* frame stepping in audio/video pipeline in PAUSED ### audio/video pipeline in PAUSED
``` ```
.-----. .-------. .------. .-------. .-----. .-------. .------. .-------.
| src | | demux | .-----. | vdec | | vsink | | src | | demux | .-----. | vdec | | vsink |
| src->sink src1->|queue|->sink src->sink | | src->sink src1->|queue|->sink src->sink |
'-----' | | '-----' '------' '-------' '-----' | | '-----' '------' '-------'
| | .------. .-------. | | .------. .-------.
| | .-----. | adec | | asink | | | .-----. | adec | | asink |
| src2->|queue|->sink src->sink | | src2->|queue|->sink src->sink |
'-------' '-----' '------' '-------' '-------' '-----' '------' '-------'
``` ```
*
- app sets the pipeline to PAUSED to block on the preroll picture - app sets the pipeline to PAUSED to block on the preroll picture
- app seeks to required position in the stream. This can be done - app seeks to required position in the stream. This can be done
@ -88,7 +86,7 @@ short segments of data in PLAYING.
there needs to be enough queueing in the pipeline to compensate there needs to be enough queueing in the pipeline to compensate
for the accumulated audio. for the accumulated audio.
- frame stepping in audio/video pipeline in PLAYING ### audio/video pipeline in PLAYING
- app sets the pipeline to PAUSED to block on the preroll picture - app sets the pipeline to PAUSED to block on the preroll picture
@ -116,23 +114,22 @@ short segments of data in PLAYING.
A new `GST_EVENT_STEP` event is introduced to start the step operation. A new `GST_EVENT_STEP` event is introduced to start the step operation.
The step event is created with the following fields in the structure: The step event is created with the following fields in the structure:
* **`format`** GST_TYPE_FORMAT: The format of the step units * **`format`** `GST_TYPE_FORMAT`: The format of the step units
* **`amount`** G_TYPE_UINT64: The amount of units to step. A 0 amount * **`amount`** `G_TYPE_UINT64`: The amount of units to step. A 0 amount
immediately completes and can be used to cancel the current step and resume immediately completes and can be used to cancel the current step and resume
normal non-stepping behaviour to the end of the segment. A -1 amount steps normal non-stepping behaviour to the end of the segment. A -1 amount steps
until the end of the segment. until the end of the segment.
* **`rate`** G_TYPE_DOUBLE: The rate at which the frames should be stepped in * **`rate`** `G_TYPE_DOUBLE`: The rate at which the frames should be stepped in
PLAYING mode. 1.0 is the normal playback speed and direction of the segment, PLAYING mode. 1.0 is the normal playback speed and direction of the segment,
2.0 is double speed. A speed of 0.0 is not allowed. When performing a flushing 2.0 is double speed. A speed of 0.0 is not allowed. When performing a flushing
step, the speed is not relevant. Note that we don't allow negative rates here, step, the speed is not relevant. Note that we don't allow negative rates here,
use a seek with a negative rate first to reverse the playback direction. use a seek with a negative rate first to reverse the playback direction.
* **`flush`** G_TYPE_BOOLEAN: when flushing is TRUE, the step is performed * **`flush`** `G_TYPE_BOOLEAN`: when flushing is TRUE, the step is performed
immediately: immediately:
*
- In the PAUSED state the pipeline loses the PAUSED state, the - In the PAUSED state the pipeline loses the PAUSED state, the
requested amount of data is skipped and the pipeline prerolls again requested amount of data is skipped and the pipeline prerolls again
when a non-intermediate step completes. When the pipeline was when a non-intermediate step completes. When the pipeline was
@ -156,14 +153,14 @@ immediately:
operation, the step operation will be performed from the position of operation, the step operation will be performed from the position of
the last PAUSED state. the last PAUSED state.
* **`intermediate`** G_TYPE_BOOLEAN: Signal that this step operation is an * **`intermediate`** `G_TYPE_BOOLEAN`: Signal that this step operation is an
intermediate step, part of a series of step operations. It is mostly intermediate step, part of a series of step operations. It is mostly
interesting for stepping in the PAUSED state because the sink will only perform interesting for stepping in the PAUSED state because the sink will only perform
a preroll after a non-intermediate step operation completes. Intermediate steps a preroll after a non-intermediate step operation completes. Intermediate steps
are useful to flush out data from other sinks in order to not cause excessive are useful to flush out data from other sinks in order to not cause excessive
queueing. In the PLAYING state the intermediate flag has no visual effect. In queueing. In the PLAYING state the intermediate flag has no visual effect. In
all states, the intermediate flag is passed to the corresponding all states, the intermediate flag is passed to the corresponding
GST_MESSAGE_STEP_DONE. `GST_MESSAGE_STEP_DONE`.
The application will create a STEP event to start or stop the stepping The application will create a STEP event to start or stop the stepping
operation. Both stepping in PAUSED and PLAYING can be performed by means operation. Both stepping in PAUSED and PLAYING can be performed by means
@ -191,15 +188,15 @@ fields.
* **`active`**: If the step was queued or activated. * **`active`**: If the step was queued or activated.
* **`format`** GST_TYPE_FORMAT: The format of the step units that queued/activated. * **`format`** `GST_TYPE_FORMAT`: The format of the step units that queued/activated.
* **`amount`** G_TYPE_UINT64: The amount of units that were queued/activated. * **`amount`** `G_TYPE_UINT64`: The amount of units that were queued/activated.
* **`rate`** G_TYPE_DOUBLE: The rate and direction at which the frames were queued/activated. * **`rate`** `G_TYPE_DOUBLE`: The rate and direction at which the frames were queued/activated.
* **`flush`** G_TYPE_BOOLEAN: If the queued/activated frames will be flushed. * **`flush`** `G_TYPE_BOOLEAN`: If the queued/activated frames will be flushed.
* **`intermediate`** G_TYPE_BOOLEAN: If this is an intermediate step operation * **`intermediate`** `G_TYPE_BOOLEAN`: If this is an intermediate step operation
that queued/activated. that queued/activated.
The `STEP_START` message is emitted 2 times: The `STEP_START` message is emitted 2 times:
@ -218,13 +215,13 @@ possible moment.
A new `GST_MESSAGE_STEP_DONE` message is created. It contains the A new `GST_MESSAGE_STEP_DONE` message is created. It contains the
following fields: following fields:
* **`format`** GST_TYPE_FORMAT: The format of the step units that completed. * **`format`** `GST_TYPE_FORMAT`: The format of the step units that completed.
* **`amount`** G_TYPE_UINT64: The amount of units that were stepped. * **`amount`** `G_TYPE_UINT64`: The amount of units that were stepped.
* **`rate`** G_TYPE_DOUBLE: The rate and direction at which the frames were stepped. * **`rate`** `G_TYPE_DOUBLE`: The rate and direction at which the frames were stepped.
* **`flush`** G_TYPE_BOOLEAN: If the stepped frames were flushed. * **`flush`** `G_TYPE_BOOLEAN`: If the stepped frames were flushed.
* **`intermediate`** G_TYPE_BOOLEAN: If this is an intermediate step operation that completed. * **`intermediate`** `G_TYPE_BOOLEAN`: If this is an intermediate step operation that completed.
* **`duration`** G_TYPE_UINT64: The total duration of the stepped units in `GST_FORMAT_TIME`. * **`duration`** `G_TYPE_UINT64`: The total duration of the stepped units in `GST_FORMAT_TIME`.
* **`eos`** G_TYPE_BOOLEAN: The step ended because of EOS. * **`eos`** `G_TYPE_BOOLEAN`: The step ended because of EOS.
The message is emitted by the element that performs the step operation. The message is emitted by the element that performs the step operation.
The purpose is to return the duration in `GST_FORMAT_TIME` of the The purpose is to return the duration in `GST_FORMAT_TIME` of the