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110 lines
3.4 KiB
Text
110 lines
3.4 KiB
Text
GStreamer: Research into encoding and muxing
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Use Cases
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---------
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This is a list of various use-cases where encoding/muxing is being
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used.
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* Transcoding
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The goal is to convert with as minimal loss of quality any input
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file for a target use.
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A specific variant of this is transmuxing (see below).
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Example applications: Arista, Transmageddon
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* Rendering timelines
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The incoming streams are a collection of various segments that need
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to be rendered.
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Those segments can vary in nature (i.e. the video width/height can
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change).
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This requires the use of identiy with the single-segment property
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activated to transform the incoming collection of segments to a
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single continuous segment.
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Example applications: PiTiVi, Jokosher
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* Encoding of live sources
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The major risk to take into account is the encoder not encoding the
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incoming stream fast enough. This is outside of the scope of
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encodebin, and should be solved by using queues between the sources
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and encodebin, as well as implementing QoS in encoders and sources
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(the encoders emitting QoS events, and the upstream elements
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adapting themselves accordingly).
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Example applications: camerabin, cheese
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* Screencasting applications
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This is similar to encoding of live sources.
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The difference being that due to the nature of the source (size and
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amount/frequency of updates) one might want to do the encoding in
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two parts:
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* The actual live capture is encoded with a 'almost-lossless' codec
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(such as huffyuv)
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* Once the capture is done, the file created in the first step is
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then rendered to the desired target format.
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Fixing sources to only emit region-updates and having encoders
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capable of encoding those streams would fix the need for the first
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step but is outside of the scope of encodebin.
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Example applications: Istanbul, gnome-shell, recordmydesktop
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* Live transcoding
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This is the case of an incoming live stream which will be
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broadcasted/transmitted live.
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One issue to take into account is to reduce the encoding latency to
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a minimum. This should mostly be done by picking low-latency
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encoders.
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Example applications: Rygel, Coherence
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* Transmuxing
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Given a certain file, the aim is to remux the contents WITHOUT
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decoding into either a different container format or the same
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container format.
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Remuxing into the same container format is useful when the file was
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not created properly (for example, the index is missing).
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Whenever available, parsers should be applied on the encoded streams
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to validate and/or fix the streams before muxing them.
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Metadata from the original file must be kept in the newly created
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file.
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Example applications: Arista, Transmaggedon
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* Loss-less cutting
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Given a certain file, the aim is to extract a certain part of the
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file without going through the process of decoding and re-encoding
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that file.
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This is similar to the transmuxing use-case.
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Example applications: PiTiVi, Transmageddon, Arista, ...
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* Multi-pass encoding
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Some encoders allow doing a multi-pass encoding.
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The initial pass(es) are only used to collect encoding estimates and
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are not actually muxed and outputted.
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The final pass uses previously collected information, and the output
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is then muxed and outputted.
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* Archiving and intermediary format
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The requirement is to have lossless
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* CD ripping
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Example applications: Sound-juicer
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* DVD ripping
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Example application: Thoggen
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