Audio-Opusfile

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lib/Audio/Opusfile.pm  view on Meta::CPAN

is returned if the stream is not seekable.

B<Warning:> If the Opus stream (or link) is concurrently multiplexed with
other logical streams (e.g., video), this uses the size of the entire
stream (or link) to compute the bitrate, not just the number of bytes
in the first logical Opus stream.

=item $of->B<bitrate_instant>

Compute the instantaneous bitrate, measured as the ratio of bits to
playable samples decoded since a) the last call to B<bitrate_instant>,
b) the last seek, or c) the start of playback, whichever was most
recent.

This will spike somewhat after a seek or at the start/end of a chain
boundary, as pre-skip, pre-roll, and end-trimming causes samples to be
decoded but not played.

=item $of->B<raw_tell>

Obtain the current value of the position indicator of I<$of>. This is
the byte position that is currently being read from.

=item $of->B<pcm_tell>

Obtain the PCM offset of the next sample to be read.

lib/Audio/Opusfile.pm  view on Meta::CPAN

of the tail of the link to which it seeks.

=item $of->B<pcm_seek>(I<$offset>)

Seek to the specified PCM offset, such that decoding will begin at
exactly the requested position. The PCM offset is in samples at 48 kHz
relative to the start of the stream.

=item $of->B<set_gain_offset>(I<$gain_type>, I<$gain_offset>)

Sets the gain to be used for decoded output.

By default, the gain in the header is applied with no additional
offset. The total gain (including header gain and/or track gain, if
applicable, and this offset), will be clamped to [-32768,32767]/256
dB. This is more than enough to saturate or underflow 16-bit PCM.

B<Note:> The new gain will not be applied to any already buffered,
decoded output. This means you cannot change it sample-by-sample, as
at best it will be updated packet-by-packet. It is meant for setting a
target volume level, rather than applying smooth fades, etc.

I<$gain_type> is one of OP_HEADER_GAIN, OP_TRACK_GAIN, or
OP_ABSOLUTE_GAIN. I<$gain_offset> is in 1/256ths of a dB.

=item $of->B<set_dither_enabled>(I<$enabled>)

Sets whether or not dithering is enabled for 16-bit decoding.

lib/Audio/Opusfile.pm  view on Meta::CPAN

uses read_float() or read_float_stereo(), or when the library has been
compiled to decode directly to fixed point, this flag has no effect.

=item $of->B<read>([I<$bufsize>])

It is recommended to use B<read_float> instead of this method if the
rest of your audio processing chain can handle floating point.

Reads more samples from the stream. I<$bufsize> is the maximum number
of samples read, and it defaults to 1048576. Returns a list whose
first element is the link index this data was decoded from, and the
rest of the elements are PCM samples, as signed 16-bit values at 48
kHz with a nominal range of [-32768,32767). Multiple channels are
interleaved using the L<Vorbis channel ordering|https://www.xiph.org/vorbis/doc/Vorbis_I_spec.html#x1-810004.3.9>.

You can use C<< $of->head($li)->channel_count >> to find out the
channel count of a given link index.

=item $of->B<read_float>([I<$bufsize>])

Like B<read>, but samples are signed floats with a nominal range of

lib/Audio/Opusfile/Head.pm  view on Meta::CPAN

=item $head->B<pre_skip>

The number of samples that should be discarded from the beginning of
the stream.

=item $head->B<input_sample_rate>

The sampling rate of the original input.

All Opus audio is coded at 48 kHz, and should also be decoded at 48
kHz for playback (unless the target hardware does not support this
sampling rate). However, this field may be used to resample the audio
back to the original sampling rate, for example, when saving the
output to a file.

=item $head->B<output_gain>

The gain to apply to the decoded output, in dB, as a Q8 value in the
range -32768...32767.

The libopusfile API will automatically apply this gain to the decoded
output before returning it, scaling it by
pow(10,output_gain/(20.0*256)).

=item $head->B<mapping_family>

The channel mapping family, in the range 0...255.

Channel mapping family 0 covers mono or stereo in a single stream.
Channel mapping family 1 covers 1 to 8 channels in one or more
streams, using the Vorbis speaker assignments. Channel mapping family