% dtas-player_protocol(7) dtas user manual % # NAME dtas-player_protocol - protocol for controling dtas-player # DESCRIPTION NOTE - NOTE - NOTE - NOTE - NOTE - NOTE - NOTE - NOTE I'm considering a heavy revamp of this protocol. The "OK" responses for a lot of commands may not be necessary since this is Unix sockets and not TCP, and I may move away from a request-response model and towards an entirely listen/notification model. I have little experience in non-TCP-based application protocols, so this is an area of experimentation for me. This must stay over Unix sockets because filesystem permissions are needed to enforce code execution permissions. dtas-player is really a shell in disguise, after all. Protocol feedback greatly appreciated, email us at dtas-all@nongnu.org ********************************************************* This gives a specification of the dtas-player protocol over a local Unix SOCK_SEQPACKET socket. The dtas-player protocol should NOT be considered stable at this point and compatibility will break. Inspiration is taken from MPRIS and MPRIS 2.0 specifications (e.g. play_pause, play, pause), and there will be a proxy in the future to support MPRIS/MPRIS 2.0 clients. The DTAS_PLAYER_SOCK is the standard environment determining the control socket for dtas-player(1). This defaults to $HOME/.dtas/player.sock if unset. Most low-level commands may be issued using the dtas-ctl(1) command. Higher-level commands such as dtas-console(1), dtas-sourceedit(1), dtas-sinkedit(1), and dtas-enq(1) also implement this protocol. # ARGUMENT TYPES - BOOLEAN - must be "true" or "false" - INTEGER - a signed integer in decimal notation (base 10) - UNSIGNED - an unsigned integer in decimal or hex notation - ENVNAME - must be a suitable environment variable (setenv(3)) - ENVVALUE - must be a suitable environment variable (setenv(3)) - COMMAND, this may be quoted string passed to sh -c "", variable/argument expansion will be performed by the shell - SOURCENAME - "sox" or "av", more backends may be supported in the future - TIMESTAMP - a time stamp formatted in HH:MM:SS.FRAC (for seeking) - TRACKID - a unique unsigned integer in decimal (base-10) representing a track in the tracklist - FILENAME - an expanded pathname relative to / is recommended since dtas-player and the client may run in different directories # VARIABLE EXPANSION For source and sink "command" arguments, the $SOXFMT and $ECAFMT environment variables are exported automatically to source to ease integration with sox(1) and ecasound(1). Both $SOXFMT and $ECAFMT are based on the configured "format" of the dtas-player (see below). For all machines, $SOXFMT defaults to: -ts32 -c2 -r44100 For little-endian machines, $ECAFMT defaults to: -fs32_le,2,44100 # COMMANDS Commands here should be alphabetized according to `LC_ALL=C sort' * cd - change the current working directory of the player * clear - clear current queue (current track/command continues running) PENDING: this may be renamed to "queue clear" or "queue-clear" * cue - display the index/offsets of the file based on the embedded cue sheet, if any * cue next - skip to the next section of the track based on the embedded cue sheet. This may skip to the next track if there is no embedded cue sheet or if playing the last (embedded) track * cue prev - skip to the previous section of the track based on the embedded cue sheet. This may just seek to the beginning if there is no embedded cue sheet or if we are playing the first (embedded) track. * cue goto INTEGER - go to the embedded track with cue index denoted by INTEGER (0 is first track as returned by "cue"). Negative values of INTEGER allows selecting track relative to the last track (-1 is the last track, -2 is the penultimate, and so on). * current - output information about the currently-playing track/command in YAML. The structure of this is unstable and subject to change. * enq FILENAME - enqueue the given FILENAME for playback An expanded (full) pathname relative to '/' is recommended, as dtas-player and the client may be in different directories. PENDING: this may be renamed to "queue add" * enq-cmd "COMMAND" - run the following command for playback. The COMMAND is expected to output audio in the audio format matching the current audio format of the player. This may be a shell pipeline and include multiple commands. The $SOXFMT and $ECAFMT variables are available here. PENDING: this may be renamed to "queue add-cmd" * env ENVTOSET=ENVVALUE ENVTOSET2=ENVVALUE2 Set environment variables. This affects all future source/sink processes as well as helper commands dtas-player may spawn (e.g. soxi(1)). Environment variables set this way are currently not preserved across invocations of dtas-player(1), but may change in the future. * env ENVTOUNSET1# ENVTOUNSET# Unset the given environment variable. PENDING: the '#' is ugly and inconsistent with the per-sink/source. env. * format FORMATARGS - configure the format between source and sink Changing this will affect the $SOXFMT and $ECAFMT environments passed to source and sink commands. Changing this implies a "restart" Changing rate to 48000 is probably useful if you plan on playing to some laptop sound cards. In all cases where "bypass" is supported, it removes the guarantee of gapless playback as the audio device(s) will likely need to be restarted. + channels=(UNSIGNED|bypass) - (default: 2 (stereo)) - number of channels to use internally. sox will internally invoke the remix effect when decoding. This supports the value "bypass" (without quotes) to avoid the automatic remix effect. Using "bypass" mode removes the guarantee of gapless playback, as the audio device will likely need to be restarted, introducing an audible gap. + endian=(big|little|swap) - (default: native) - there is probably no point in changing this unless you output over a network sink to a machine of different endianess. + bits=(UNSIGNED|bypass) - (default: implied from type) - sample precision (decoded) This may be pointless and removed in the future, since the sample precision is implied from type. This supports the value of "bypass" to avoid dither/truncation in later stages. + rate=(UNSIGNED|bypass) - (default: 44100) - sample rate of audio Typical values of rate are 44100, 48000, 88200, 96000. Not all DSP effects are compatible with all sampling rates/channels. This supports the value of "bypass" as well to avoid introducing software resamplers into the playback chain. + type=(s16|s24|s32|u16|u24|u32|f32|f64) - (default: s32) change the raw PCM format. s32 currently offers the best performance when only sox/play are used. f32 may offer better performance if piping to/from non-sox applications (e.g. ecasound) * pause - pause playback Player pause state is preserved across dtas-player invocations. * play - restart playback from pause. Playback sinks will yield control of the audio playback device once no source is playing. * play_pause - toggle the play/pause state. This starts playback if paused, and pauses playback if playing. * queue cat - dump the contents of the queue as YAML This may include arbitrary commands to be executed, filenames, and offsets for playback. The format is not intended to be stable and subject to internal changes in dtas-player. * restart - restarts all processes in the current pipeline. Playback will be momentarily interrupted while this change occurs. This is necessary if one of the commands (e.g. sox or ecasound) or loaded libraries (e.g. a LADSPA plugin) is upgraded. Use "source restart" instead to only restart the source chain, leaving the sinks untouched. * rg RGARGS - configure ReplayGain support All FLOAT values may be adjusted via '+=' or '-=' instead of simple assignment ('='). If RGARGS is empty, the current rg state of non-default values will be dumped in YAML. + fallback_gain=FLOAT (-6.0) - dB value Adjust the volume by this level (usually negative) for tracks missing ReplayGain tags. This is useful when the queue contains a mix of tracks with and without ReplayGain tags. + fallback_track=BOOLEAN (true) When in album_gain mode, fallback to track_gain if the REPLAYGAIN_ALBUM_GAIN metadata is missing. + mode=(album_gain|track_gain|track_norm|album_norm|off) This controls the ReplayGain tag to use. The *_norm options are used for peak normalization and not commonly found in other players. + preamp=FLOAT (0) - dB value Adjust the album_gain or track_gain amount by this value (in dB). + norm_level=FLOAT (1.0 == dBFS) Controls the level to normalize to when using album_norm or track_norm. * seek [+-]TIMESTAMP - seek the current track to a specified time. This is passed directly as the first argument for the sox(1) "trim" command. See the sox(1) manpage for details. Seeking to a relative time is also supported by prefixing the time with '+' or '-' * skip - abort current track/command (via closing the output pipe) Running the "clear" command before this will abort playback. * sink ls - list names of current sinks * sink cat SINKNAME - dump SINKNAME config in YAML * sink rm SINKNAME - remove SINKNAME * sink ed SINKNAME SINKARGS - create/edit SINKNAME This currently does not restart running (active) sinks. This will stop active sinks if active is set to false, and start active sinks if active is set to true. See dtas-sinkedit(1) for an example of using this. + command=COMMAND - change the command-line used for playback + active=BOOLEAN - whether or not the sink will be in use (default: false) + env.ENVNAME=ENVVALUE - set ENVNAME to ENVVALUE for the sink process + env#ENVNAME - unset ENVNAME in the sink process (only) + prio=INTEGER - priority of the sink, lower values run first + nonblock=BOOLEAN - drop audio data to avoid holding back other sinks + pipe_size=UNSIGNED - set the size of the pipe for the sink (Linux-only) * source cat SOURCENAME - dump the current source command and env in YAML * source ed SOURCENAME SOURCEARGS - edit the source parameters. This changes here will immediately restart the source process. See the code for dtas-sourceedit(1) for an example of using this. + command=COMMAND - change the command-line used to decode audio + env.ENVNAME=ENVVALUE - set ENVNAME to ENVVALUE for the source process + env#ENVNAME - unset ENVNAME in the source process (only) + tryorder=INTEGER - lower values are tried first PENDING: tryorder here is wrong and may be removed or changed. We need to account for at least two variables input file: 1. input type (flac/opus/mp3/etc) 2. transport protocol (local FS/http/ftp/sftp/etc) * source ls - dump the names of sources sorted by tryorder * source restart - restart the current source command This can be useful if the source file is changed during playback and the current player process is holding onto an unlinked inode. This is advantageous over a full "restart" as there is no audible gap on most systems. * state dump [FILENAME] Immediately dump the state of the player. If a FILENAME is specified, the state is written to that file. Otherwise, the default state file (configured via DTAS_PLAYER_STATE environment variable, defaulting to ~/.dtas/player_state.yml) is written to. This does not use fsync(2), users requiring fsync should open(2) that file and fsync(2) it themselves if necessary. * tl add FILENAME [TRACKID [BOOLEAN]] - add files to the tracklist With one arg, adds FILENAME to the head of the tracklist. If TRACKID is specified, FILENAME is added immediately after TRACKID on the existing tracklist. The final BOOLEAN argument replaces the currently playing track with the newly-added one. Returns the TRACKID of the newly added track * tl clear - clear current tracklist * tl current - display the pathname to the currently playing track * tl current-id - display the TRACKID of the currently playing track * tl remove TRACKID - remove the track with the given TRACKID from the track list and returns the FILENAME if successful * tl get [TRACKIDS] returns a list of TRACKIDS mapped to shell-escaped filenames. * tl goto TRACKID [TIMESTAMP] - plays the given TRACKID An optional timestamp may be added to prevent playing the same part(s) repeatedly * tl max [MAXIMUM] - sets or gets the maximum number of tracks allowed in the tracklist * tl next - jump to the next track in the tracklist * tl prev - jump to the previous track in the tracklist * tl repeat [BOOLEAN|1] - show/or change repeat status of the tracklist. With no args, this will show "true", "false", or "1" If set to "1", dtas-player will repeat the current track. Returns the previous repeat status. * tl shuffle [BOOLEAN] - show/or change the current shuffle status of the tracklist. Returns the previous shuffle status. * tl swap TRACKID_A TRACKID_B - swaps the positions of two tracks. * tl tracks returns a list of all TRACKIDS in the tracklist * trim [off|TBEG [TLEN]] Limits playback of all tracks in the tracklist to the time starting at TBEG and ending after TLEN has elapsed. Not specifying TLEN will cause sox. Like the sox "trim" effect, prefixing TLEN with a '=' will be interpreted as an absolute stop time. Both TBEG and TLEN should be specified in seconds, not sample counts. Specifying "off" (without quotes) disables trim. This feature is intended to allow users to "zoom-in" on a particular portion of a track to tweak parameters (either with dtas-sourceedit(1) or via playback of splitfx YAML files) and often combined with looping the tracklist (via "tl repeat"). * watch - adds the client to the passive watch list for notifications. It is recommended clients issue no further commands and open another client socket to issue non-watch commands. # CONTACT All feedback welcome via plain-text mail to: \ Mailing list archives available at and \ No subscription is necessary to post to the mailing list. # COPYRIGHT Copyright 2013-2016 all contributors .\ License: GPL-3.0+