Media logging manual


User submitting debug info


  • get samples
  • run a script
  • submit that directory

This is detailed in tools/ffmpeg/readme_run_tests.txt.

Changing code in pyglet ffmpeg subsystem

Preparation like in readme_run_tests.txt, optionally install the library bokeh ( for visualization support.

The basic flow goes as:

  • initialize the active session subsystem: set environment variable pyglet_mp_samples_dir to the desired samples_dir.

  • record a session with the initial state: new <session> [playlist]
  • Follow this workflow

    while True:
        edit code
        commit to hg
        record a new session:
   new <new session> [playlist]
        look at the last session reports in samples_dir/session/reports
        especially 00_summary.txt, which shows defects stats and list condensed
            info about any sample failing;
        then to look more details look at the individual reports.
        compare with prev sessions if desired:
   <session1> <session2>
        render additional reports:
        or visualize the data collected with:
        if results are as wanted, break
    done, you may want to delete sessions for intermediate commits

It is possible to return to a previous session to request additional reports: activate <session> ...

You can list the known sessions for the current samples_dir with: list


All this debugging machinery depends on a detailed and accurate capture of media_player related state, currently in examples/ and

Modifications in those modules may require matching modifications in pyglet/media/sources/, and further propagation to other modules.

Changing the debug code for pyglet ffmpeg

For initial debugging of debug code, where there are misspellings and trivial errors to weed out, creating a new session for each run may be inconvenient.

The flag dev_debug can be set to true in the session configuration file; this will allow to rewrite the session.

Keep in mind that some raw data will be stale or misleading:

  • The ones captured at session creation time (currently and pyglet_changeset)
  • The collected crashes info (new crashes will not be seen)
  • If crashes before doing any writing, the state recording will be the previous recording.

The reports using that stale raw data will obviously report stale data.

So it is a good idea to switch to a normal workflow as soon as posible (simply creating a new session and deleting the special session).


If playlist_file is not specified, then all files in samples_dir, except for the files with extension “.dbg”, “.htm”, “.html”, “.json”, “.log”, “.pkl”, “.py”, “.txt” will make the implicit playlist; subdirectories of samples_dir will not be explored.

If a playlist_file is specified, then it should contain one sample name per line; a sanity check will be performed ensuring no blacklisted extension is used, and that the sample exists in samples_dir.

Once the playlist_file is used in new a copy is writen to the session raw data directory, and this copy will be the authoritative playlist for the session; playlist_file can be deleted if desired.

Specifying a playlist is useful in development to restrict the tests to samples relevant to the feature or issue under work.

The session name will be used to create a samples_dir subdir to store the test results, hence it should be different of previous sessions names, and it must not contain slashes, /, backslashes \ or characters forbidden in directory names.

Active session

Most commands and subcommands target the currently active session.

A session becomes active when

  • a new session [playlist] is issued
  • a activate session is issued

The current implementation relies in two pieces of data to determine the active session

  • the environment variable pyglet_mp_samples_dir specifies samples_dir, the directory where all the media samples reside. Under the current paths schema is also where session data will be stored, one subdir per session.
  • a file activation.json in samples_dir storing the name for the current active session.

Notice that the second precludes running two commands in parallel targeting two different sessions in the same sample_dir.

The concept of active session plus the enforced path schema avoids the need to provide paths at each command invocation, making for less errors, easier docs and less typing.

Commands Summary

Primary commands

They are the ones normally used by developers, : session creation, activation, protection, status and list all. : plays session’s samples, reports results. : produces the specified report for the specified sample. : translates the event stream to a stream of media_player state, useful to pass to other software. : visualization of data collected for the specified sample.

Helper commands

Somehow an artifact of development, can help in testing the debugging subsystem. is basically + + When trying to change it is easier to first adapt the relevant helper. : plays active session samples, recording media_player state along the play. : plays again samples that have been seen always crashing, hoping to get a recording with no crash. Motivated by early tests on Ubuntu, where sometimes (but not always) a sample will crash the media_player. : using the raw data produced by the two previous commands elaborates some reports, aiming to give an idea of how well the run was and what samples should be investigated.

Data directory layout

samples_dir/ : directory where the samples live, also used to store
               sessions data
    <session name>/ : directory to store session info, one per session,
                      named as the session.
        dbg/ : recording of media_player events captured while playing a
               sample, one per sample, named as sample.dbg; additional
               versioning info, other raw data collected.
            _crashes_light.pkl : pickle with info for retry crashed
            <one .dbg file per sample in the session playlist, named sample.dbg>
        reports/ : human readable reports rendered from the raw data (.txt),
                   visualizations (.html), intermediate data used by other
        configuration.json : session configuration info, mostly permissions
    activation.json : holds the name of current active session
    <sample> : one for each sample

A subdirectory of samples_dir is detected as a session dir if:

  • it is a direct child of session dir
  • it has a configuration.json file


  • it should be hard to rewrite the .dbg files (recordings of media_player states)
  • think of dev analyzing data sent by an user.

Code Layout and conventions

The emerging separation of responsabilities goes like

Scripts (commands)

Structured as:

  • uses if __main__ idiom to allow use as module (testing, sharing)

  • sysargs_to_mainargs(): sys.argv translation to main params

  • main(...)

    • params validation and translation to adequate code entities (uses module fs).
    • translates exceptions to prints (uses module mpexceptions)
    • short chain of instantiations / function calls to accomplish the command goals, no logic or calculations here.
  • other functions and classes: code specific to this command, delegates as much as possible to modules.

When two scripts use some related but not identical functionality, these parts can be moved to another module. Example: at first summarize had the code to collect defects stats, later, when compare was writen, the module extractors was added and the defect collection stats code moved to that module.

If script B needs a subset of unchanged script A functionality, it imports A and uses what it needs. Example is retry_crashed, will call into playmany.

Because of the last point, some scripts will also be listed as modules.



Accumulation of debug events while playing media_player, saves when sample’s play ends


Defines the events that modify media_player state. Defines which events are potential defects. Gives the low level support to extract info from the recorded data.

For new code here, keep accepting and returning only data structures, no paths or files.


Path building for entities into a session directory should be delegated to fs.PathServices. Session’s creation, activation and management at start of fs. Versions capture are handled at start of module fs. Utility functions to load - save at the end of fs.

While there isn’t a Session object, in practice the code identifies and provides access to a particular session data by handling a fs.PathServices instance.


Analyzes a media_player recording to build specific info on behalf of reporters. Uses instrumentation to get input data about the media_player state sequence seen while playing a sample. Defines object types to collect some specific info about a replay.


Formats as text info captured / generated elsewhere.


Defines exceptions generated by code in the ffmpeg debug subsystem.

Scripts that also acts as modules


Renders the media player’s debug info to a format more suitable to postprocess in a spreadsheets or other software, particularly to get a data visualization. (used by


Produces media_player debug recordings. Runs python scripts as subprocesses with a timeout (used by

Commands detailed

Usage: sample

Renders media player’s internal state graphically using bokeh.


sample: sample to report

The output will be written to session’s output dir under reports/sample.timeline.html.

Notice the plot can be zoomed live with the mouse wheel, but you must click the button that looks as a distorted OP; it also does pan with mouse drag.

Example: small.mp4

will write the output to report/small.mp4.timeline.html.

Usage: --reldir=relpath other_session

Builds a reports comparing the active session with other_session.

Outputs to samples_dir/relpath/comparison_<session>_<other_session>.txt.

Usage: subcommand [args]


new session [playlist] : Creates a new session, sets it as the active one
activate session : activates a session
deactivate : no session will be active
protect [target]: forbids overwrite of session data
status : prints configuration for the active session
help [subcommand] : prints help for the given subcommand or topic
list : list all sessions associated the current samples_dir

Creates and manages pyglet media_player debug session configurations.

Most commands and subcommands need an environment variable pyglet_mp_samples_dir to be set to the directory where the media samples reside.

The configuration stores some values used when other commands are executed, mostly protection status.

This command can be called both as or, they do the same.

alias for


Uses media_player to play a sequence of samples and record debug info.

A session must be active, see command If the active configuration has disallowed dbg overwrites it will do nothing.

If a playlist was provided at session creation, then only the samples in the playlist will be played, otherwise all files in samples_dir.

Usage: sample report_name

Generates a report from the debugging info recorded while playing sample.


sample: sample to report
report_name: desired report, one of
    "anomalies": Start, end and interesting events
    "all": All data is exposed as text
    "counter": How many occurrences of each defect

The report will be written to session’s output dir under reports/sample.report_name.txt.


report anomalies small.mp4

will write the report anomalies to report/small.mp4.anomalies.txt.

The authoritative list of reports available comes from reports.available_reports

Usage: [--clean] [max_retries]

Inspects the raw data collected to get the list of samples that crashed the last time they were played. Then it replays those samples, recording new raw data for them.

The process is repeated until all samples has a recording with no crashes or the still crashing samples were played max_tries times in this command run.

Notice that only samples recorded as crashing in the last run are retried.

A configuration must be active, see command

Besides the updated debug recordings, a state is build and saved:

total_retries: total retries attempted, including previous runs
sometimes_crashed: list of samples that crashed one time but later
                   completed a play
always_crashed: list of samples that always crashed


--clean: discards crash data collected in a previous run
max_retries: defaults to 5

Usage: [samples_dir]

Plays media samples with the pyglet media_player, recording debug information for each sample played and writing reports about the data captured.


samples_dir: directory with the media samples to play

If no samples_dir is provided the active session is the target. If an explicit playlist was specified when creating the session, then only the samples in the playlist will be played, otherwise all samples in samples_dir will be played.

If sample_dir is provided, a session named testrun_00 (_01, _02, … if that name was taken) will be created, with no explicit playlist, and then the command operates as in the previous case.

Output files will be into:

samples_dir/session/dbg : binary capture of media_player events, other raw
                          data captured
samples_dir/session/reports : human readable reports


This script will refuse to overwrite an existing test_run results.

Output files will be into subdirectories:


Each sample will generate a sample.dbg file storing the sequence of player debug events seen while playing the sample. It is simply a pickle of a list of tuples, each tuple an event. There are not meant for direct human use, but to run some analyzers to render useful reports.

A crash_retries.pkl file, a pickle of (total_retries, sometimes_crashed, still_crashing) <-> (int, set, set).

A captured at session creation to track hw & sw.

A pyglet hg revision captured at session creation.


Human readable outputs, described in command

Later a user can generate visualizations and additional reports that will be stored in this directory


Summarizes the session info collected with playmany and retry_crashes.

A configuration must be active, see command

If a playlist was provided at session creation, then only the samples in the playlist will be played, otherwise all files in samples_dir.

Produces human readable reports, constructed from the .dbg files.

Output will be in


The files in that directory will be

00_summary.txt , which provides:

  • basics defects stats over all samples
  • a paragraph for each non perfect sample play with the count of each anomaly observed

03_pyglet_info.txt , output giving OS, python version, etc (as captured at session creation).

04_pyglet_hg_revision.txt , pyglet hg revision if running from a repo clone, non writen if no repo (as captured at session creation).

sample_name.all.txt and sample_name.anomalies.txt for each sample that played non perfect.

sample_name.all.txt has all info in the sample_name.dbg in human readable form, that is, the sequence of player’s internal events along the play.

sample_name.anomalies.txt is a reduced version of the .all. variant: normal events are not shown, only anomalies.

Usage: sample [output_format]

Renders the media player’s debug info to a format more suitable to postprocess in a spreadsheets or other software, particularly to get a data visualization.

See output details in the manual.


sample: sample to report
output_format : one of { "csv", "pkl"}, by default saves as .pkl (pickle)

The output will be written to session’s output dir under reports/sample.timeline.[.pkl or .csv].

Example: small.mp4

will write the output to report/small.mp4.timeline.pkl.


.csv sample is currently not implemented.


Samples should be small, at the moment I suggest an arbitrary 2MB 2 minutes limit. The samples dir contains a _sources.txt which lists from where each sample comes.


Samples are not ‘certified to be compliant with the specification’.

When possible, samples should be played with non ffmpeg software for incidental confirmation of well formed

*.mp4, *.3gp played well with Windows Media Player for win7

*.ogv, *. webm played well with Firefox 54.0

*.flv, *.mkv played well with VLC Media player, but VLC uses ffmpeg

Surely the samples set will be refined as time goes.

pycharm notes

For examples/video_ffmpeg module visibility and code completion, that directory should be a ‘content root’ in pycharm settings | ‘project structure’; as projects roots cannot nest, the pyglet working copy cannot be a ‘content root’, I removed it; I added also working_copy/pyglet as another ‘content root’ so pycharm plays well also en the library proper. This with pycharm 2017.2