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docs: Gram and nit fixes for part-buffering.txt
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@ -6,7 +6,7 @@ core that can be used by plugins and applications.
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The purpose of buffering is to accumulate enough data in a pipeline so that
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playback can occur smoothly and without interruptions. It is typically done
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when reading from a (slow) and non-live network source but can also be used for
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when reading from a (slow) non-live network source but can also be used for
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live sources.
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We want to be able to implement the following features:
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@ -41,12 +41,12 @@ Some use cases:
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the sinks.
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- When the high watermark is hit, a BUFFERING message with 100% will be
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posted, which instructs the application to continue playback.
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- When during playback, the low watermark is hit, the queue will start posting
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- When the low watermark is hit during playback, the queue will start posting
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BUFFERING messages again, making the application PAUSE the pipeline again
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until the high watermark is hit again. This is called the rebuffering
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stage.
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- during playback, the queue level will fluctuate between the high and the
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low watermark as a way to compensate for network irregularities.
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- During playback, the queue level will fluctuate between the high and
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low watermarks as a way to compensate for network irregularities.
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This buffering method is usable when the demuxer operates in push mode.
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Seeking in the stream requires the seek to happen in the network source.
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@ -63,14 +63,14 @@ Some use cases:
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file
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In this case, we know the server is streaming a fixed length file to the
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client. The application can choose to download the file on disk. The buffer
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client. The application can choose to download the file to disk. The buffer
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element will provide a push or pull based srcpad to the demuxer to navigate in
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the downloaded file.
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This mode is only suitable when the client can determine the length of the
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file on the server.
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In this case, buffering messages will be emited as usual when the requested
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In this case, buffering messages will be emitted as usual when the requested
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range is not within the downloaded area + buffersize. The buffering message
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will also contain an indication that incremental download is being performed.
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This flag can be used to let the application control the buffering in a more
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@ -96,7 +96,7 @@ Some use cases:
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This mode is suitable for all live streams.
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As with the incremental download mode, buffering messages are emited along
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As with the incremental download mode, buffering messages are emitted along
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with an indication that timeshifting download is in progress.
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@ -106,7 +106,7 @@ Some use cases:
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the playback elements. This latency can be introduced by a queue (such as a
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jitterbuffer) or by other means (in the audiosink).
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Buffering messages can be emited in those live pipelines as well and serve as
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Buffering messages can be emitted in those live pipelines as well and serve as
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an indication to the user of the latency buffering. The application usually
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does not react to these buffering messages with a state change.
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@ -115,7 +115,7 @@ Messages
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~~~~~~~~
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A GST_MESSAGE_BUFFERING must be posted on the bus when playback temporarily
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stops to buffer and when buffering finishes. When percentage field in the
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stops to buffer and when buffering finishes. When the percentage field in the
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BUFFERING message is 100, buffering is done. Values less than 100 mean that
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buffering is in progress.
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@ -131,24 +131,23 @@ are added to the buffering message:
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"buffering-mode", GST_TYPE_BUFFERING_MODE,
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enum { "stream", "download", "timeshift", "live" }
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- gives the buffering mode in use. See above for an explanation of the
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different modes of buffering. This field can be used to let the
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- Buffering mode in use. See above for an explanation of the
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different alternatives. This field can be used to let the
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application have more control over the buffering process.
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"avg-in-rate", G_TYPE_INT
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- gives the average input buffering speed in bytes/second. -1 is unknown.
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- Average input buffering speed in bytes/second. -1 is unknown.
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This is the average number of bytes per second that is received on the
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buffering element input (sink) pads. It is a measurement of the network
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speed in most cases.
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"avg-out-rate", G_TYPE_INT
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- gives the average consumption speed in bytes/second. -1 is unknown.
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- Average consumption speed in bytes/second. -1 is unknown.
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This is the average number of bytes per second that is consumed by the
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downstream element of the buffering element.
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"buffering-left", G_TYPE_INT64
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- gives the estimated time that bufferring will take in milliseconds.
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-1 unknown.
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- Estimated time that buffering will take in milliseconds. -1 is unknown.
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This is measured based on the avg-in-rate and the filled level of the
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queue. The application can use this hint to update the GUI about the
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estimated remaining time that buffering will take.
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@ -156,36 +155,37 @@ are added to the buffering message:
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Application
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~~~~~~~~~~~
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While data is buffered, the pipeline should remain in the PAUSED state. It is
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While data is buffered the pipeline should remain in the PAUSED state. It is
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also possible that more data should be buffered while the pipeline is PLAYING,
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in which case the pipeline should be PAUSED until the buffering finished.
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in which case the pipeline should be PAUSED until the buffering finishes.
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BUFFERING messages can be posted while the pipeline is prerolling. The
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application should not set the pipeline to PLAYING before a BUFFERING message
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with 100 percent value is received, which might only happen after the pipeline
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prerolled.
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with a 100 percent value is received, which might only happen after the pipeline
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prerolls.
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An exception is made for live pipelines. The application may not change
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the state of a live pipeline when a buffering message is received. Usually these
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buffering messages contain the "buffering-mode" = "live".
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The buffering message can also instruct the application to switch to a periodical
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BUFFERING query instead to more precisely control the buffering process. The
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application can, for example, choose to not act on the BUFFERING message with
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100 percent fill level to resume playback but instead use the estimated download
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time to resume playback to get uninterrupted playback.
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The buffering message can also instruct the application to switch to a
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periodical BUFFERING query instead, so it can more precisely control the
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buffering process. The application can, for example, choose not to act on the
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BUFFERING complete message (buffer-percent = 100) to resume playback but use
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the estimated download time instead, resuming playback when it has determined
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that it should be able to provide uninterrupted playback.
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Buffering Query
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~~~~~~~~~~~~~~~
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In addition to the BUFFERING messages posted by the buffering elements we want
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In addition to the BUFFERING messages posted by the buffering elements, we want
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to be able to query the same information from the application. We also want to
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be able to present the user with information about the downloaded range in the
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file so that the GUI can react on it.
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In addition to all the fields present in the buffering message, the BUFFERING
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query contains the following field, which indicate the available downloaded
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query contains the following field, which indicates the available downloaded
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range in a specific format and the estimated time to complete:
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"busy", G_TYPE_BOOLEAN
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@ -205,7 +205,7 @@ range in a specific format and the estimated time to complete:
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- gives the estimated download time in milliseconds. -1 unknown.
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When the size of the downloaded file is known, this value will contain
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the latest estimate of the remaining download time. This value is usualy
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the latest estimate of the remaining download time. This value is usually
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only filled for the "download" buffering mode. The application can use
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this information to estimate the amount of remaining time to download the
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complete file.
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