[pulseaudio-discuss] [RFC PATCH] Log PCM samples to files

[Vincent Becker]

Hi,

I recently created a new PA module (module-log-pcm) which is able to log PCM samples from any source/sink and its corresponding outputs/inputs. For testing audio quality, checking signal processing or verifying the right implementation of a sound device mixed in PA, application fields are many. One just needs to give a parameter list depending on what is wished to be logged. During the process, an audio tree, or parts of it, is probed and logged for post-treatment purposes. For design needs, sources and sinks are designated by "ends" and source outputs/sink inputs by "ports".

Module-log-pcm's main characteristics are :

- Core principles : given a source or a sink name, a working source output used only for log is created and plugged (to the sink.monitor in case of a sink). PCM samples are handled in the push callback and can be redirected to any log device. For ports (SO/SI), the only information available is the connected sink/source and the index. As a result, hooks in the pulsecore have been necessary to capture PCM chunks, before resampling for sink inputs and after resampling for source outputs.

- Choice between a local or remote target : this functionnality uses pa_object object-oriented library. Depending if the log is saved in a wave file or written to any other type of file descriptor (type of target), a "serializer" implementation does the logging of PCM samples. Each serializer (local-file-serializer or remote-device-serializer) is defined within PA_DEFINE_PUBLIC_CLASS that allows a kind of function polymorphism. Wave files are named per end or port names, e.g. "sink_name.wav" and for ports, the index is appended to the log file name, e.g. for index 2 :  "sink_name_2.wav".
For local log : libsndfile is used to log in wav files in the same manner as pacat. A directory is specified in parameter, where all the wav files can be stored.
For remote log (in opposite to local log..) : a header is attached at the beginning of the log file, containing sample spec informations, signal strength (volume ?), source/sink name...

- Log of sources/sinks with or without their outputs/inputs :
All or none of the ports can be logged by means of an option specified at the module loading : trace_ports=<yes/no> .

- Management of put, move, unlink events :
If an end is declared to be logged, it will be monitored whatever its creation comes after or before the loading of module-log-pcm, and for move events, a new log file will be created after each move to help distinguish the samples. The "move" prefix along with a number is appended to the log file name. Also when a device is unlinked, its corresponding log file will be closed.

- Support of most of the data sample formats :
Data formats like PA_SAMPLE_S24_32NE can also be logged, but a realignment of the 24 bits on 32 bits is necessary to ensure correct audio restitution in a wave file.


These are examples of logging different sinks/sources to a target :

Log specified sinks and one source with their ports, in wav files to directory wav_log_files :
Load module-log-pcm sinks_to_log=alsa_output.intel_mfld_msic_audio.earphone,sink.music sources_to_log=source.record trace_ports=yes log_target=/home/vincent/wav_log_files/

We shall get wave files like these : 
alsa_output.intel_mfld_msic_audio.earphone.wav
alsa_output.intel_mfld_msic_audio.earphone_0.wav
sink.music.wav
sink_music_1.wav
source.record.wav
source_record_2.wav

Log specified sinks and sources (note the .monitor is in the list of sources) without their ports to a remote device :
Load module-log-pcm sinks_to_log=alsa_output.intel_mfld_msic_audio.earphone sources_to_log=sink.hsandihf.monitor,source.record trace_ports=no log_target=/dev/remote_snd


The development might look a bit ackward and certainly still needs modifications but it macan be seen as the first stone of experimental logging..
Please feel free to comment.

Thanks,
Vincent

Vincent Becker (1):
  Log module: new module to log PCM chunks.

 src/Makefile.am                            |   11 +-
 src/modules/log/local-file-serializer.c    |  181 +++++
 src/modules/log/local-file-serializer.h    |   47 ++
 src/modules/log/log-pcm-serializer.c       |   50 ++
 src/modules/log/log-pcm-serializer.h       |   52 ++
 src/modules/log/module-log-pcm.c           | 1113 ++++++++++++++++++++++++++++
 src/modules/log/pcm-logger-data.h          |   57 ++
 src/modules/log/remote-device-serializer.c |  140 ++++
 src/modules/log/remote-device-serializer.h |   48 ++
 src/pulsecore/core.h                       |    2 +
 src/pulsecore/sink-input.c                 |   18 +
 src/pulsecore/sink-input.h                 |    5 +
 src/pulsecore/source-output.c              |   27 +-
 src/pulsecore/source-output.h              |    6 +
 14 files changed, 1753 insertions(+), 4 deletions(-)
 create mode 100755 src/modules/log/local-file-serializer.c
 create mode 100755 src/modules/log/local-file-serializer.h
 create mode 100755 src/modules/log/log-pcm-serializer.c
 create mode 100755 src/modules/log/log-pcm-serializer.h
 create mode 100755 src/modules/log/module-log-pcm.c
 create mode 100755 src/modules/log/pcm-logger-data.h
 create mode 100755 src/modules/log/remote-device-serializer.c
 create mode 100755 src/modules/log/remote-device-serializer.h

-- 
1.7.2.3

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