AUDIO FILTERS ============= Audio filters allow you to modify the audio stream and its properties. The syntax is: ``--af=`` Setup a chain of audio filters. .. note:: To get a full list of available audio filters, see ``--af=help``. Also, keep in mind that most actual filters are available via the ``lavfi`` wrapper, which gives you access to most of libavfilter's filters. This includes all filters that have been ported from MPlayer to libavfilter. You can also set defaults for each filter. The defaults are applied before the normal filter parameters. ``--af-defaults=`` Set defaults for each filter. Audio filters are managed in lists. There are a few commands to manage the filter list: ``--af-add=`` Appends the filters given as arguments to the filter list. ``--af-pre=`` Prepends the filters given as arguments to the filter list. ``--af-del=`` Deletes the filters at the given indexes. Index numbers start at 0, negative numbers address the end of the list (-1 is the last). ``--af-clr`` Completely empties the filter list. Available filters are: ``lavrresample[=option1:option2:...]`` This filter uses libavresample (or libswresample, depending on the build) to change sample rate, sample format, or channel layout of the audio stream. This filter is automatically enabled if the audio output does not support the audio configuration of the file being played. It supports only the following sample formats: u8, s16, s32, float. ``filter-size=`` Length of the filter with respect to the lower sampling rate. (default: 16) ``phase-shift=`` Log2 of the number of polyphase entries. (..., 10->1024, 11->2048, 12->4096, ...) (default: 10->1024) ``cutoff=`` Cutoff frequency (0.0-1.0), default set depending upon filter length. ``linear`` If set then filters will be linearly interpolated between polyphase entries. (default: no) ``no-detach`` Do not detach if input and output audio format/rate/channels match. (If you just want to set defaults for this filter that will be used even by automatically inserted lavrresample instances, you should prefer setting them with ``--af-defaults=lavrresample:...``.) ``normalize=`` Whether to normalize when remixing channel layouts (default: yes). This is e.g. applied when downmixing surround audio to stereo. The advantage is that this guarantees that no clipping can happen. Unfortunately, this can also lead to too low volume levels. Whether you enable or disable this is essentially a matter of taste, but the default uses the safer choice. ``o=`` Set AVOptions on the SwrContext or AVAudioResampleContext. These should be documented by FFmpeg or Libav. ``lavcac3enc[=tospdif[:bitrate[:minch]]]`` Encode multi-channel audio to AC-3 at runtime using libavcodec. Supports 16-bit native-endian input format, maximum 6 channels. The output is big-endian when outputting a raw AC-3 stream, native-endian when outputting to S/PDIF. If the input sample rate is not 48 kHz, 44.1 kHz or 32 kHz, it will be resampled to 48 kHz. ``tospdif=`` Output raw AC-3 stream if ``no``, output to S/PDIF for pass-through if ``yes`` (default). ``bitrate=`` The bitrate use for the AC-3 stream. Set it to 384 to get 384 kbps. The default is 640. Some receivers might not be able to handle this. Valid values: 32, 40, 48, 56, 64, 80, 96, 112, 128, 160, 192, 224, 256, 320, 384, 448, 512, 576, 640. The special value ``auto`` selects a default bitrate based on the input channel number: :1ch: 96 :2ch: 192 :3ch: 224 :4ch: 384 :5ch: 448 :6ch: 448 ``minch=`` If the input channel number is less than ````, the filter will detach itself (default: 3). ``equalizer=g1:g2:g3:...:g10`` 10 octave band graphic equalizer, implemented using 10 IIR band-pass filters. This means that it works regardless of what type of audio is being played back. The center frequencies for the 10 bands are: === ========== No. frequency === ========== 0 31.25 Hz 1 62.50 Hz 2 125.00 Hz 3 250.00 Hz 4 500.00 Hz 5 1.00 kHz 6 2.00 kHz 7 4.00 kHz 8 8.00 kHz 9 16.00 kHz === ========== If the sample rate of the sound being played is lower than the center frequency for a frequency band, then that band will be disabled. A known bug with this filter is that the characteristics for the uppermost band are not completely symmetric if the sample rate is close to the center frequency of that band. This problem can be worked around by upsampling the sound using a resampling filter before it reaches this filter. ``:::...:`` floating point numbers representing the gain in dB for each frequency band (-12-12) .. admonition:: Example ``mpv --af=equalizer=11:11:10:5:0:-12:0:5:12:12 media.avi`` Would amplify the sound in the upper and lower frequency region while canceling it almost completely around 1 kHz. ``channels=nch[:routes]`` Can be used for adding, removing, routing and copying audio channels. If only ```` is given, the default routing is used. It works as follows: If the number of output channels is greater than the number of input channels, empty channels are inserted (except when mixing from mono to stereo; then the mono channel is duplicated). If the number of output channels is less than the number of input channels, the exceeding channels are truncated. ```` number of output channels (1-8) ```` List of ``,`` separated routes, in the form ``from1-to1,from2-to2,...``. Each pair defines where to route each channel. There can be at most 8 routes. Without this argument, the default routing is used. Since ``,`` is also used to separate filters, you must quote this argument with ``[...]`` or similar. .. admonition:: Examples ``mpv --af=channels=4:[0-1,1-0,2-2,3-3] media.avi`` Would change the number of channels to 4 and set up 4 routes that swap channel 0 and channel 1 and leave channel 2 and 3 intact. Observe that if media containing two channels were played back, channels 2 and 3 would contain silence but 0 and 1 would still be swapped. ``mpv --af=channels=6:[0-0,0-1,0-2,0-3] media.avi`` Would change the number of channels to 6 and set up 4 routes that copy channel 0 to channels 0 to 3. Channel 4 and 5 will contain silence. .. note:: You should probably not use this filter. If you want to change the output channel layout, try the ``format`` filter, which can make mpv automatically up- and downmix standard channel layouts. ``format=format:srate:channels:out-format:out-srate:out-channels`` Does not do any format conversion itself. Rather, it may cause the filter system to insert necessary conversion filters before or after this filter if needed. It is primarily useful for controlling the audio format going into other filters. To specify the format for audio output, see ``--audio-format``, ``--audio-samplerate``, and ``--audio-channels``. This filter is able to force a particular format, whereas ``--audio-*`` may be overridden by the ao based on output compatibility. All parameters are optional. The first 3 parameters restrict what the filter accepts as input. They will therefore cause conversion filters to be inserted before this one. The ``out-`` parameters tell the filters or audio outputs following this filter how to interpret the data without actually doing a conversion. Setting these will probably just break things unless you really know you want this for some reason, such as testing or dealing with broken media. ```` Force conversion to this format. Use ``--af=format=format=help`` to get a list of valid formats. ```` Force conversion to a specific sample rate. The rate is an integer, 48000 for example. ```` Force mixing to a specific channel layout. See ``--audio-channels`` option for possible values. ```` ```` ```` *NOTE*: this filter used to be named ``force``. The old ``format`` filter used to do conversion itself, unlike this one which lets the filter system handle the conversion. ``volume[=[:...]]`` Implements software volume control. Use this filter with caution since it can reduce the signal to noise ratio of the sound. In most cases it is best to use the *Master* volume control of your sound card or the volume knob on your amplifier. *NOTE*: This filter is not reentrant and can therefore only be enabled once for every audio stream. ```` Sets the desired gain in dB for all channels in the stream from -200 dB to +60 dB, where -200 dB mutes the sound completely and +60 dB equals a gain of 1000 (default: 0). ``replaygain-track`` Adjust volume gain according to the track-gain replaygain value stored in the file metadata. ``replaygain-album`` Like replaygain-track, but using the album-gain value instead. ``replaygain-preamp`` Pre-amplification gain in dB to apply to the selected replaygain gain (default: 0). ``replaygain-clip=yes|no`` Prevent clipping caused by replaygain by automatically lowering the gain (default). Use ``replaygain-clip=no`` to disable this. ``replaygain-fallback`` Gain in dB to apply if the file has no replay gain tags. This option is always applied if the replaygain logic is somehow inactive. If this is applied, no other replaygain options are applied. ``softclip`` Turns soft clipping on. Soft-clipping can make the sound more smooth if very high volume levels are used. Enable this option if the dynamic range of the loudspeakers is very low. *WARNING*: This feature creates distortion and should be considered a last resort. ``s16`` Force S16 sample format if set. Lower quality, but might be faster in some situations. ``detach`` Remove the filter if the volume is not changed at audio filter config time. Useful with replaygain: if the current file has no replaygain tags, then the filter will be removed if this option is enabled. (If ``--softvol=yes`` is used and the player volume controls are used during playback, a different volume filter will be inserted.) .. admonition:: Example ``mpv --af=volume=10.1 media.avi`` Would amplify the sound by 10.1 dB and hard-clip if the sound level is too high. ``pan=n:[]`` Mixes channels arbitrarily. Basically a combination of the volume and the channels filter that can be used to down-mix many channels to only a few, e.g. stereo to mono, or vary the "width" of the center speaker in a surround sound system. This filter is hard to use, and will require some tinkering before the desired result is obtained. The number of options for this filter depends on the number of output channels. An example how to downmix a six-channel file to two channels with this filter can be found in the examples section near the end. ```` Number of output channels (1-8). ```` A list of values ``[L00,L01,L02,...,L10,L11,L12,...,Ln0,Ln1,Ln2,...]``, where each element ``Lij`` means how much of input channel i is mixed into output channel j (range 0-1). So in principle you first have n numbers saying what to do with the first input channel, then n numbers that act on the second input channel etc. If you do not specify any numbers for some input channels, 0 is assumed. Note that the values are separated by ``,``, which is already used by the option parser to separate filters. This is why you must quote the value list with ``[...]`` or similar. .. admonition:: Examples ``mpv --af=pan=1:[0.5,0.5] media.avi`` Would downmix from stereo to mono. ``mpv --af=pan=3:[1,0,0.5,0,1,0.5] media.avi`` Would give 3 channel output leaving channels 0 and 1 intact, and mix channels 0 and 1 into output channel 2 (which could be sent to a subwoofer for example). .. note:: If you just want to force remixing to a certain output channel layout, it is easier to use the ``format`` filter. For example, ``mpv '--af=format=channels=5.1' '--audio-channels=5.1'`` would always force remixing audio to 5.1 and output it like this. ``delay[=[ch1,ch2,...]]`` Delays the sound to the loudspeakers such that the sound from the different channels arrives at the listening position simultaneously. It is only useful if you have more than 2 loudspeakers. ``[ch1,ch2,...]`` The delay in ms that should be imposed on each channel (floating point number between 0 and 1000). To calculate the required delay for the different channels, do as follows: 1. Measure the distance to the loudspeakers in meters in relation to your listening position, giving you the distances s1 to s5 (for a 5.1 system). There is no point in compensating for the subwoofer (you will not hear the difference anyway). 2. Subtract the distances s1 to s5 from the maximum distance, i.e. ``s[i] = max(s) - s[i]; i = 1...5``. 3. Calculate the required delays in ms as ``d[i] = 1000*s[i]/342; i = 1...5``. .. admonition:: Example ``mpv --af=delay=[10.5,10.5,0,0,7,0] media.avi`` Would delay front left and right by 10.5 ms, the two rear channels and the subwoofer by 0 ms and the center channel by 7 ms. ``drc[=method:target]`` Applies dynamic range compression. This maximizes the volume by compressing the audio signal's dynamic range. (Formerly called ``volnorm``.) ```` Sets the used method. 1 Use a single sample to smooth the variations via the standard weighted mean over past samples (default). 2 Use several samples to smooth the variations via the standard weighted mean over past samples. ```` Sets the target amplitude as a fraction of the maximum for the sample type (default: 0.25). .. note:: This filter can cause distortion with audio signals that have a very large dynamic range. ``scaletempo[=option1:option2:...]`` Scales audio tempo without altering pitch, optionally synced to playback speed (default). This works by playing 'stride' ms of audio at normal speed then consuming 'stride*scale' ms of input audio. It pieces the strides together by blending 'overlap'% of stride with audio following the previous stride. It optionally performs a short statistical analysis on the next 'search' ms of audio to determine the best overlap position. ``scale=`` Nominal amount to scale tempo. Scales this amount in addition to speed. (default: 1.0) ``stride=`` Length in milliseconds to output each stride. Too high of a value will cause noticeable skips at high scale amounts and an echo at low scale amounts. Very low values will alter pitch. Increasing improves performance. (default: 60) ``overlap=`` Percentage of stride to overlap. Decreasing improves performance. (default: .20) ``search=`` Length in milliseconds to search for best overlap position. Decreasing improves performance greatly. On slow systems, you will probably want to set this very low. (default: 14) ``speed=`` Set response to speed change. tempo Scale tempo in sync with speed (default). pitch Reverses effect of filter. Scales pitch without altering tempo. Add this to your ``input.conf`` to step by musical semi-tones:: [ multiply speed 0.9438743126816935 ] multiply speed 1.059463094352953 .. warning:: Loses sync with video. both Scale both tempo and pitch. none Ignore speed changes. .. admonition:: Examples ``mpv --af=scaletempo --speed=1.2 media.ogg`` Would play media at 1.2x normal speed, with audio at normal pitch. Changing playback speed would change audio tempo to match. ``mpv --af=scaletempo=scale=1.2:speed=none --speed=1.2 media.ogg`` Would play media at 1.2x normal speed, with audio at normal pitch, but changing playback speed would have no effect on audio tempo. ``mpv --af=scaletempo=stride=30:overlap=.50:search=10 media.ogg`` Would tweak the quality and performance parameters. ``mpv --af=format=float,scaletempo media.ogg`` Would make scaletempo use float code. Maybe faster on some platforms. ``mpv --af=scaletempo=scale=1.2:speed=pitch audio.ogg`` Would play media at 1.2x normal speed, with audio at normal pitch. Changing playback speed would change pitch, leaving audio tempo at 1.2x. ``rubberband`` High quality pitch correction with librubberband. This can be used in place of ``scaletempo``, and will be used to adjust audio pitch when playing at speed different from normal. This filter has a number of sub-options. You can list them with ``mpv --af=rubberband=help``. This will also show the default values for each option. The options are not documented here, because they are merely passed to librubberband. Look at the librubberband documentation to learn what each option does: http://breakfastquay.com/rubberband/code-doc/classRubberBand_1_1RubberBandStretcher.html (The mapping of the mpv rubberband filter sub-option names and values to those of librubberband follows a simple pattern: ``"Option" + Name + Value``.) ``lavfi=graph`` Filter audio using FFmpeg's libavfilter. ```` Libavfilter graph. See ``lavfi`` video filter for details - the graph syntax is the same. .. warning:: Don't forget to quote libavfilter graphs as described in the lavfi video filter section. ``o=`` AVOptions.