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doc/muxers/fifo: review documentation
Apply consistency fixes, sort options, clarify example.
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Stefano Sabatini
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149
doc/muxers.texi
149
doc/muxers.texi
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@ -1421,104 +1421,115 @@ ffmpeg -i INPUT -s:v 720x480 -pix_fmt yuv411p -r 29.97 -ac 2 -ar 48000 -y out.dv
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@anchor{fifo}
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@section fifo
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FIFO (First-In First-Out) muxer.
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The fifo pseudo-muxer allows the separation of encoding and muxing by using
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first-in-first-out queue and running the actual muxer in a separate thread. This
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is especially useful in combination with the @ref{tee} muxer and can be used to
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send data to several destinations with different reliability/writing speed/latency.
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The @samp{fifo} pseudo-muxer allows the separation of encoding and
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muxing by using a first-in-first-out queue and running the actual muxer
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in a separate thread.
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API users should be aware that callback functions (interrupt_callback,
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io_open and io_close) used within its AVFormatContext must be thread-safe.
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This is especially useful in combination with
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the @ref{tee} muxer and can be used to send data to several
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destinations with different reliability/writing speed/latency.
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The behavior of the fifo muxer if the queue fills up or if the output fails is
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selectable,
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The target muxer is either selected from the output name or specified
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through the @option{fifo_format} option.
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The behavior of the @samp{fifo} muxer if the queue fills up or if the
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output fails (e.g. if a packet cannot be written to the output) is
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selectable:
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@itemize @bullet
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@item
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Output can be transparently restarted with configurable delay between
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retries based on real time or time of the processed stream.
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@item
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output can be transparently restarted with configurable delay between retries
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based on real time or time of the processed stream.
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@item
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encoding can be blocked during temporary failure, or continue transparently
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dropping packets in case fifo queue fills up.
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Encoding can be blocked during temporary failure, or continue transparently
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dropping packets in case the FIFO queue fills up.
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@end itemize
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API users should be aware that callback functions
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(@code{interrupt_callback}, @code{io_open} and @code{io_close}) used
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within its @code{AVFormatContext} must be thread-safe.
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@subsection Options
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@table @option
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@item fifo_format
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@item attempt_recovery @var{bool}
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If failure occurs, attempt to recover the output. This is especially
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useful when used with network output, since it makes it possible to
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restart streaming transparently. By default this option is set to
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@code{false}.
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@item drop_pkts_on_overflow @var{bool}
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If set to @code{true}, in case the fifo queue fills up, packets will
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be dropped rather than blocking the encoder. This makes it possible to
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continue streaming without delaying the input, at the cost of omitting
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part of the stream. By default this option is set to @code{false}, so in
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such cases the encoder will be blocked until the muxer processes some
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of the packets and none of them is lost.
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@item fifo_format @var{format_name}
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Specify the format name. Useful if it cannot be guessed from the
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output name suffix.
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@item queue_size
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Specify size of the queue (number of packets). Default value is 60.
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@item format_opts @var{options}
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Specify format options for the underlying muxer. Muxer options can be
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specified as a list of @var{key}=@var{value} pairs separated by ':'.
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@item format_opts
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Specify format options for the underlying muxer. Muxer options can be specified
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as a list of @var{key}=@var{value} pairs separated by ':'.
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@item max_recovery_attempts @var{count}
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Set maximum number of successive unsuccessful recovery attempts after
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which the output fails permanently. By default this option is set to
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@code{0} (unlimited).
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@item drop_pkts_on_overflow @var{bool}
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If set to 1 (true), in case the fifo queue fills up, packets will be dropped
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rather than blocking the encoder. This makes it possible to continue streaming without
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delaying the input, at the cost of omitting part of the stream. By default
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this option is set to 0 (false), so in such cases the encoder will be blocked
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until the muxer processes some of the packets and none of them is lost.
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@item attempt_recovery @var{bool}
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If failure occurs, attempt to recover the output. This is especially useful
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when used with network output, since it makes it possible to restart streaming transparently.
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By default this option is set to 0 (false).
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@item max_recovery_attempts
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Sets maximum number of successive unsuccessful recovery attempts after which
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the output fails permanently. By default this option is set to 0 (unlimited).
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@item recovery_wait_time @var{duration}
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Waiting time before the next recovery attempt after previous unsuccessful
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recovery attempt. Default value is 5 seconds.
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@item recovery_wait_streamtime @var{bool}
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If set to 0 (false), the real time is used when waiting for the recovery
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attempt (i.e. the recovery will be attempted after at least
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recovery_wait_time seconds).
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If set to 1 (true), the time of the processed stream is taken into account
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instead (i.e. the recovery will be attempted after at least @var{recovery_wait_time}
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seconds of the stream is omitted).
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By default, this option is set to 0 (false).
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@item queue_size @var{size}
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Specify size of the queue as a number of packets. Default value is
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@code{60}.
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@item recover_any_error @var{bool}
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If set to 1 (true), recovery will be attempted regardless of type of the error
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causing the failure. By default this option is set to 0 (false) and in case of
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certain (usually permanent) errors the recovery is not attempted even when
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@var{attempt_recovery} is set to 1.
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If set to @code{true}, recovery will be attempted regardless of type
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of the error causing the failure. By default this option is set to
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@code{false} and in case of certain (usually permanent) errors the
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recovery is not attempted even when the @option{attempt_recovery}
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option is set to @code{true}.
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@item recovery_wait_streamtime @var{bool}
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If set to @code{false}, the real time is used when waiting for the
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recovery attempt (i.e. the recovery will be attempted after the time
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specified by the @option{recovery_wait_time} option).
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If set to @code{true}, the time of the processed stream is taken into
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account instead (i.e. the recovery will be attempted after discarding
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the packets corresponding to the @option{recovery_wait_time} option).
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By default this option is set to @code{false}.
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@item recovery_wait_time @var{duration}
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Specify waiting time in seconds before the next recovery attempt after
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previous unsuccessful recovery attempt. Default value is @code{5}.
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@item restart_with_keyframe @var{bool}
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Specify whether to wait for the keyframe after recovering from
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queue overflow or failure. This option is set to 0 (false) by default.
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queue overflow or failure. This option is set to @code{false} by default.
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@item timeshift @var{duration}
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Buffer the specified amount of packets and delay writing the output. Note that
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@var{queue_size} must be big enough to store the packets for timeshift. At the
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end of the input the fifo buffer is flushed at realtime speed.
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Buffer the specified amount of packets and delay writing the
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output. Note that the value of the @option{queue_size} option must be
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big enough to store the packets for timeshift. At the end of the input
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the fifo buffer is flushed at realtime speed.
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@end table
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@subsection Examples
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@subsection Example
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@itemize
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@item
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Stream something to rtmp server, continue processing the stream at real-time
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rate even in case of temporary failure (network outage) and attempt to recover
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streaming every second indefinitely.
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Use @command{ffmpeg} to stream to an RTMP server, continue processing
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the stream at real-time rate even in case of temporary failure
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(network outage) and attempt to recover streaming every second
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indefinitely:
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@example
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ffmpeg -re -i ... -c:v libx264 -c:a aac -f fifo -fifo_format flv -map 0:v -map 0:a
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-drop_pkts_on_overflow 1 -attempt_recovery 1 -recovery_wait_time 1 rtmp://example.com/live/stream_name
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ffmpeg -re -i ... -c:v libx264 -c:a aac -f fifo -fifo_format flv \
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-drop_pkts_on_overflow 1 -attempt_recovery 1 -recovery_wait_time 1 \
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-map 0:v -map 0:a rtmp://example.com/live/stream_name
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@end example
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@end itemize
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@section flv
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Adobe Flash Video Format muxer.
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