% dtas-player_protocol(7) dtas user manual =head1 NAME dtas-player_protocol - protocol for controling dtas-player =head1 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 L 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 L. This defaults to $HOME/.dtas/player.sock if unset. Most low-level commands may be issued using the L command. Higher-level commands such as L, L, L, and L also implement this protocol. =head1 ARGUMENT TYPES =over =item BOOLEAN - must be "true" or "false" =item INTEGER - a signed integer in decimal notation (base 10) =item UNSIGNED - an unsigned integer in decimal or hex notation =item ENVNAME - must be a suitable environment variable (setenv(3)) =item ENVVALUE - must be a suitable environment variable (setenv(3)) =item COMMAND - command to run This may be quoted string passed to sh -c "". Variable/argument expansion will be performed by the shell =item SOURCENAME - "sox" or "av", more backends may be supported in the future =item TIMESTAMP - a time stamp formatted in HH:MM:SS.FRAC (for seeking) =item TRACKID - a unique unsigned integer in decimal (base-10) This represents a track in the tracklist =item FILENAME An expanded pathname relative to / is recommended since dtas-player and the client may run in different directories =back =head1 VARIABLE EXPANSION For source and sink "command" arguments, the $SOXFMT and $ECAFMT environment variables are exported automatically to source to ease integration with L and L. 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 =head1 COMMANDS Commands here should be alphabetized according to `LC_ALL=C sort' =over =item cd - change the current working directory of the player =item clear - clear current queue (current track/command continues running) PENDING: this may be renamed to "queue clear" or "queue-clear" =item cue - display the index/offsets of the embedded CUE sheet =item cue next - skip to the next cue sheet offset This may skip to the next track if there is no embedded cue sheet or if playing the last (embedded) track =item cue prev - skip to the previous cue sheet offset This may just seek to the beginning if there is no embedded cue sheet or if we are playing the first (embedded) track. =item cue goto INTEGER [TIMESTAMP] - go to the 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). The optional TIMESTAMP allows starting the index track at a given point, negative values allow going to a set point before the given index. In other words: "cue goto 1 -5" seeks to the last five seconds of the first track while "cue goto 1 5" seeks to the fifth second of the second track =item cue seek TIMESTAMP - seek within the current cue index Like the normal "seek" command, but this confines the seeking within the currently playing index. As with "seek", "+" and "-" prefixes allow seeking relative to the currently playing position Using a "=-" prefix allows seeking to the previous track within the CUE sheet, relative to the currently playing track. =item current - output information about the current track/command in YAML The structure of this is unstable and subject to change. =item 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" =item 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" =item 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. L). Environment variables set this way are currently not preserved across invocations of L, but may change in the future. =item env ENVTOUNSET1# ENVTOUNSET# Unset the given environment variable. PENDING: the '#' is ugly and inconsistent with the per-sink/source. env. =item 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. =over =item 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. =item 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. =item 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. =item 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. =item 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) =back =item pause - pause playback Player pause state is preserved across dtas-player invocations. =item play - restart playback from pause Playback sinks will yield control of the audio playback device once no source is playing. =item play_pause - toggle the play/pause state This starts playback if paused, and pauses playback if playing. =item 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. =item 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. =item 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. =over =item 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. =item fallback_track=BOOLEAN (true) When in album_gain mode, fallback to track_gain if the REPLAYGAIN_ALBUM_GAIN metadata is missing. =item 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. =item preamp=FLOAT (0) - dB value Adjust the album_gain or track_gain amount by this value (in dB). =item norm_level=FLOAT (1.0 == dBFS) Controls the level to normalize to when using album_norm or track_norm. =back =item seek [+-]TIMESTAMP - seek the current track to a specified time. This is passed directly as the first argument for the L "trim" command. See the L manpage for details. Seeking to a relative time is also supported by prefixing the time with '+' or '-' =item skip - abort current track/command This is accomplished via closing the output pipe. Running the "clear" command before this will abort playback. =item sink ls - list names of current sinks =item sink cat SINKNAME - dump SINKNAME config in YAML =item sink rm SINKNAME - remove SINKNAME =item 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. =over =item command=COMMAND - change the command-line used for playback =item active=BOOLEAN - whether or not the sink will be in use (default: false) =item env.ENVNAME=ENVVALUE - set ENVNAME to ENVVALUE for the sink process =item env#ENVNAME - unset ENVNAME in the sink process (only) =item prio=INTEGER - priority of the sink, lower values run first =item nonblock=BOOLEAN - drop audio data to avoid holding back other sinks =item pipe_size=UNSIGNED - set the size of the pipe for the sink (Linux-only) =back =item source cat SOURCENAME - dump the current source command and env in YAML =item 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. =over =item command=COMMAND - change the command-line used to decode audio =item env.ENVNAME=ENVVALUE - set ENVNAME to ENVVALUE for the source process =item env#ENVNAME - unset ENVNAME in the source process (only) =item tryorder=INTEGER - lower values are tried first =back PENDING: tryorder here is wrong and may be removed or changed. We need to account for at least two variables input file: =over =item 1. input type (flac/opus/mp3/etc) =item 2. transport protocol (local FS/http/ftp/sftp/etc) =back =item source ls Dump the names of sources sorted by tryorder =item 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. =item 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 L, users requiring fsync should L that file and L it themselves if necessary. =item 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 =item tl clear Clear current tracklist =item tl consume [BOOLEAN] Show/or change consume status of the tracklist. Enabling this causes tracks to be deleted from the tracklist after they are played or skipped. With no args, this will show "true" or "false =item tl current Display the pathname to the currently playing track =item tl current-id Display the TRACKID of the currently playing track =item tl remove TRACKID Remove the track with the given TRACKID from the track list and returns the FILENAME if successful =item tl get [TRACKIDS] Returns a list of TRACKIDS mapped to shell-escaped filenames. =item tl goto TRACKID [TIMESTAMP] Plays the given TRACKID. An optional timestamp may be added to prevent playing the same part(s) repeatedly =item tl max [MAXIMUM] Sets or gets the maximum number of tracks allowed in the tracklist =item tl next Jump to the next track in the tracklist =item tl prev Jump to the previous track in the tracklist =item 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. =item tl shuffle [BOOLEAN] Show/or change the current shuffle status of the tracklist. Returns the previous shuffle status. =item tl swap TRACKID_A TRACKID_B Swaps the positions of two tracks. =item tl tracks Returns a list of all TRACKIDS in the tracklist =item 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 L or via playback of splitfx YAML files) and often combined with looping the tracklist (via "tl repeat"). =item 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. =back =head1 CONTACT All feedback welcome via plain-text mail to: L Mailing list archives available at L and L No subscription is necessary to post to the mailing list. =head1 COPYRIGHT Copyright 2013-2016 all contributors L License: GPL-3.0+ L