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doc/encoders/libopus: clarify lowdelay and cutoff options

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Extend descriptions for the application=lowdelay and cutoff options.
Based on notes by Mingye Wang.

Address issues:
http://trac.ffmpeg.org/ticket/10330
http://trac.ffmpeg.org/ticket/10343
This commit is contained in:
Stefano Sabatini 2023-08-26 15:45:33 +02:00
parent 7449a00d2d
commit 00eb4966aa
2 changed files with 6 additions and 3 deletions
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7
doc/encoders.texi
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@ -977,14 +977,17 @@ Favor improved speech intelligibility.
@item audio
Favor faithfulness to the input (the default).
@item lowdelay
Restrict to only the lowest delay modes.
Restrict to only the lowest delay modes by disabling voice-optimized
modes.
@end table
@item cutoff (N.A.)
Set cutoff bandwidth in Hz. The argument must be exactly one of the
following: 4000, 6000, 8000, 12000, or 20000, corresponding to
narrowband, mediumband, wideband, super wideband, and fullband
respectively. The default is 0 (cutoff disabled).
respectively. The default is 0 (cutoff disabled). Note that libopus
forces a wideband cutoff for bitrates < 15 kbps, unless CELT-only
(@option{application} set to @samp{lowdelay}) mode is used.
@item mapping_family (@emph{mapping_family})
Set channel mapping family to be used by the encoder. The default value of -1

2
libavcodec/libopusenc.c
View File

@ -547,7 +547,7 @@ static const AVOption libopus_options[] = {
{ "application", "Intended application type", OFFSET(application), AV_OPT_TYPE_INT, { .i64 = OPUS_APPLICATION_AUDIO }, OPUS_APPLICATION_VOIP, OPUS_APPLICATION_RESTRICTED_LOWDELAY, FLAGS, "application" },
{ "voip", "Favor improved speech intelligibility", 0, AV_OPT_TYPE_CONST, { .i64 = OPUS_APPLICATION_VOIP }, 0, 0, FLAGS, "application" },
{ "audio", "Favor faithfulness to the input", 0, AV_OPT_TYPE_CONST, { .i64 = OPUS_APPLICATION_AUDIO }, 0, 0, FLAGS, "application" },
{ "lowdelay", "Restrict to only the lowest delay modes", 0, AV_OPT_TYPE_CONST, { .i64 = OPUS_APPLICATION_RESTRICTED_LOWDELAY }, 0, 0, FLAGS, "application" },
{ "lowdelay", "Restrict to only the lowest delay modes, disable voice-optimized modes", 0, AV_OPT_TYPE_CONST, { .i64 = OPUS_APPLICATION_RESTRICTED_LOWDELAY }, 0, 0, FLAGS, "application" },
{ "frame_duration", "Duration of a frame in milliseconds", OFFSET(frame_duration), AV_OPT_TYPE_FLOAT, { .dbl = 20.0 }, 2.5, 120.0, FLAGS },
{ "packet_loss", "Expected packet loss percentage", OFFSET(packet_loss), AV_OPT_TYPE_INT, { .i64 = 0 }, 0, 100, FLAGS },
{ "fec", "Enable inband FEC. Expected packet loss must be non-zero", OFFSET(fec), AV_OPT_TYPE_BOOL, { .i64 = 0 }, 0, 1, FLAGS },