Playing Sound and Video¶
pyglet can play many audio and video formats. Audio is played back with either OpenAL, XAudio2, DirectSound, or Pulseaudio, permitting hardware-accelerated mixing and surround-sound 3D positioning. Video is played into OpenGL textures, and so can be easily manipulated in real-time by applications and incorporated into 3D environments.
Decoding of compressed audio and video is provided by FFmpeg v4 or v5, an optional component available for Linux, Windows and Mac OS X. FFmpeg needs to be installed separately.
If FFmpeg is not present, pyglet will at a minimum be able to play WAV files only. Depending on the OS, an additional limited amount of compressed formats may also be supported, but only WAV is guaranteed (see “Supported media types ” below). the This may be sufficient for many applications that require only a small number of short sounds, in which case those applications need not distribute FFmpeg.
Audio drivers¶
pyglet can use OpenAL, XAudio2, DirectSound, or Pulseaudio to play back audio. Only one
of these drivers can be used in an application. In most cases you won’t need
to concern yourself with choosing a driver, but you can manually select one if
desired. This must be done before the pyglet.media
module is loaded.
The available drivers depend on your operating system:
The audio driver can be set through the audio
key of the
pyglet.options
dictionary. For example:
pyglet.options['audio'] = ('openal', 'pulse', 'xaudio2', 'directsound', 'silent')
This tells pyglet to try using the OpenAL driver first, and if not available
to try Pulseaudio, XAudio2 and DirectSound in that order. If all else fails,
no driver will be instantiated. The audio
option can be a list of any of these
strings, giving the preference order for each driver:
String Audio driver openal
OpenAL directsound
DirectSound xaudio2
XAudio2 pulse
Pulseaudio silent
No audio output
You must set the audio
option before importing pyglet.media
.
You can alternatively set it through an environment variable;
see Environment settings.
The following sections describe the requirements and limitations of each audio driver.
XAudio2¶
XAudio2 is only available on Windows Vista and above and is the replacement of DirectSound. This provides hardware accelerated audio support for newer operating systems.
Note that in some stripped down versions of Windows 10, XAudio2 may not be available until the required DLL’s are installed.
DirectSound¶
DirectSound is available only on Windows, and is installed by default. pyglet uses only DirectX 7 features. On Windows Vista, DirectSound does not support hardware audio mixing or surround sound.
OpenAL¶
OpenAL is included with Mac OS X. Windows users can download a generic driver
from openal.org, or from their sound device’s manufacturer. Most Linux
distributions will have OpenAL available in the repositories for download.
For example, Ubuntu users can apt install libopenal1
.
Pulse¶
Pulseaudio can also be used directly on Linux, and is installed by default with most modern Linux distributions. Pulseaudio does not support positional audio, and is limited to stereo. It is recommended to use OpenAL if positional audio is required.
[1] | (1, 2) OpenAL is not installed by default on Windows, nor in many Linux distributions. It can be downloaded separately from your audio device manufacturer or openal.org |
Supported media types¶
Windows and Linux both support a limited amount of compressed audio types, without the need for FFmpeg. While FFmpeg supports a large array of formats and codecs, it may be an unnecessarily large dependency when simple audio playback is needed on these operating systems.
These formats are supported natively under the following systems and codecs:
Windows Media Foundation¶
Supported on Windows operating systems.
The following are supported on Windows Vista and above:
- MP3
- WMA
- ASF
- SAMI/SMI
The following are supported on Windows 7 and above:
- 3G2/3GP/3GP2/3GP
- AAC/ADTS
- AVI
- M4A/M4V/MOV/MP4
The following is undocumented but known to work on Windows 10:
- FLAC
Please note that any video playback done through WMF is limited in codec support and is not hardware accelerated. It should only be used for simple or small videos. FFmpeg is recommended for all other purposes.
GStreamer¶
Supported on Linux operating systems that have the GStreamer installed. Please note that the associated Python packages for gobject & gst are also required. This varies by distribution, but will often already be installed along with GStreamer.
- MP3
- FLAC
- OGG
- M4A
PyOgg¶
Supported on Windows, Linux, and Mac operating systems.
PyOgg is a lightweight Python library that provides Python bindings for Opus, Vorbis, and FLAC codecs.
Pyglet now provides a wrapper to support PyOgg. Since not all operating systems can decode the same audio formats natively, it can often be a hassle to choose an audio format that is truely cross platform with a small footprint. This wrapper was created to help with that issue.
Supports the following formats:
- OGG
- FLAC
- OPUS
Refer to their installation guide found here: https://pyogg.readthedocs.io/en/latest/installation.html
FFmpeg¶
FFmpeg requires an external dependency, please see installation instructions in the next section below.
With FFmpeg, many common and less-common formats are supported. Due to the large number of combinations of audio and video codecs, options, and container formats, it is difficult to provide a complete yet useful list. Some of the supported audio formats are:
- AU
- MP2
- MP3
- OGG/Vorbis
- WAV
- WMA
Some of the supported video formats are:
- AVI
- DivX
- H.263
- H.264
- MPEG
- MPEG-2
- OGG/Theora
- Xvid
- WMV
- Webm
For a complete list, see the FFmpeg sources. Otherwise, it is probably simpler
to try playing back your target file with the media_player.py
example.
New versions of FFmpeg as they are released may support additional formats, or fix errors in the current implementation.
FFmpeg installation¶
You can install FFmpeg for your platform by following the instructions found in the FFmpeg download page. You must choose the shared build for the targeted OS with the architecture similar to the Python interpreter.
Currently Pyglet supports versions 4.x and 5.x of FFmpeg.
Choose the correct architecture depending on the targeted Python interpreter. If you’re shipping your project with a 32 bits interpreter, you must download the 32 bits shared binaries.
On Windows, the usual error message when the wrong architecture was downloaded is:
WindowsError: [Error 193] %1 is not a valid Win32 application
Finally make sure you download the shared builds, not the static or the dev builds.
For Mac OS and Linux, the library is usually already installed system-wide. It may be easiest to list FFmpeg as a requirement for your project, and leave it up to the user to ensure that it is installed. For Windows users, it’s not recommended to install the library in one of the windows sub-folders.
Instead we recommend to use the pyglet.options
search_local_libs
:
import pyglet
pyglet.options['search_local_libs'] = True
This will allow pyglet to find the FFmpeg binaries in the lib
sub-folder
located in your running script folder.
Another solution is to manipulate the environment variable. On Windows you can add the dll location to the PATH:
os.environ["PATH"] += "path/to/ffmpeg"
For Linux and Mac OS:
os.environ["LD_LIBRARY_PATH"] += ":" + "path/to/ffmpeg"
- ..note:: If your project is going to reply on FFmpeg, it’s a good idea to
- check at runtime that FFmpeg is being properly detected. This can be
done with a call to
pyglet.media.have_ffmpeg()
. If not True you can show a message and exit gracefully, rather than crashing later when failing to load media files.
Loading media¶
Audio and video files are loaded in the same way, using the
pyglet.media.load()
function, providing a filename:
source = pyglet.media.load('explosion.wav')
If the media file is bundled with the application, consider using the
resource
module (see Application resources).
The result of loading a media file is a
Source
object. This object provides useful
information about the type of media encoded in the file, and serves as an
opaque object used for playing back the file (described in the next section).
The load()
function will raise a
MediaException
if the format is unknown.
IOError
may also be raised if the file could not be read from disk.
Future versions of pyglet will also support reading from arbitrary file-like
objects, however a valid filename must currently be given.
The length of the media file is given by the
duration
property, which returns the media’s
length in seconds.
Audio metadata is provided in the source’s
audio_format
attribute, which is None
for
silent videos. This metadata is not generally useful to applications. See
the AudioFormat
class documentation for details.
Video metadata is provided in the source’s
video_format
attribute, which is None
for
audio files. It is recommended that this attribute is checked before
attempting play back a video file – if a movie file has a readable audio
track but unknown video format it will appear as an audio file.
You can use the video metadata, described in a
VideoFormat
object, to set up display of the video
before beginning playback. The attributes are as follows:
Attribute Description width
,height
Width and height of the video image, in pixels. sample_aspect
The aspect ratio of each video pixel.
You must take care to apply the sample aspect ratio to the video image size for display purposes. The following code determines the display size for a given video format:
def get_video_size(width, height, sample_aspect):
if sample_aspect > 1.:
return width * sample_aspect, height
elif sample_aspect < 1.:
return width, height / sample_aspect
else:
return width, height
Media files are not normally read entirely from disk; instead, they are streamed into the decoder, and then into the audio buffers and video memory only when needed. This reduces the startup time of loading a file and reduces the memory requirements of the application.
However, there are times when it is desirable to completely decode an audio file in memory first. For example, a sound that will be played many times (such as a bullet or explosion) should only be decoded once. You can instruct pyglet to completely decode an audio file into memory at load time:
explosion = pyglet.media.load('explosion.wav', streaming=False)
The resulting source is an instance of StaticSource
,
which provides the same interface as a StreamingSource
.
You can also construct a StaticSource
directly from an
already- loaded Source
:
explosion = pyglet.media.StaticSource(pyglet.media.load('explosion.wav'))
Audio Synthesis¶
In addition to loading audio files, the pyglet.media.synthesis
module is available for simple audio synthesis. There are several basic
waveforms available, including:
These waveforms can be constructed by specifying a duration, frequency, and sample rate. At a minimum, a duration is required. For example:
sine = pyglet.media.synthesis.Sine(3.0, frequency=440, sample_rate=44800)
For shaping the waveforms, several simple envelopes are available. These envelopes affect the amplitude (volume), and can make for more natural sounding tones. You first create an envelope instance, and then pass it into the constructor of any of the above waveforms. The same envelope instance can be passed to any number of waveforms, reducing duplicate code when creating multiple sounds. If no envelope is used, all waveforms will default to the FlatEnvelope of maximum amplitude, which esentially has no effect on the sound. Check the module documentation of each Envelope to see which parameters are available.
An example of creating an envelope and waveforms:
adsr = pyglet.media.synthesis.ADSREnvelope(attack=0.05, decay=0.2, release=0.1)
saw = pyglet.media.synthesis.Sawtooth(duration=1.0, frequency=220, envelope=adsr)
The waveforms you create with the synthesis module can be played like any other loaded sound. See the next sections for more detail on playback.
Simple audio playback¶
Many applications, especially games, need to play sounds in their entirety without needing to keep track of them. For example, a sound needs to be played when the player’s space ship explodes, but this sound never needs to have its volume adjusted, or be rewound, or interrupted.
pyglet provides a simple interface for this kind of use-case. Call the
play()
method of any Source
to play it immediately and completely:
explosion = pyglet.media.load('explosion.wav', streaming=False)
explosion.play()
You can call play()
on any
Source
, not just
StaticSource
.
The return value of play()
is a
Player
, which can either be
discarded, or retained to maintain control over the sound’s playback.
Controlling playback¶
You can implement many functions common to a media player using the
Player
class. Use of this class is also necessary for video playback. There are no
parameters to its construction:
player = pyglet.media.Player()
A player will play any source that is queued on it. Any number of sources can be queued on a single player, but once queued, a source can never be dequeued (until it is removed automatically once complete). The main use of this queueing mechanism is to facilitate “gapless” transitions between playback of media files.
The queue()
method is used to queue
a media on the player - a StreamingSource
or a
StaticSource
. Either you pass one instance, or you
can also pass an iterable of sources. This provides great flexibility. For
instance, you could create a generator which takes care of the logic about
what music to play:
def my_playlist():
yield intro
while game_is_running():
yield main_theme
yield ending
player.queue(my_playlist())
When the game ends, you will still need to call on the player:
player.next_source()
The generator will pass the ending
media to the player.
A StreamingSource
can only ever be queued on one
player, and only once on that player. StaticSource
objects can be queued any number of times on any number of players. Recall
that a StaticSource
can be created by passing
streaming=False
to the pyglet.media.load()
method.
In the following example, two sounds are queued onto a player:
player.queue(source1)
player.queue(source2)
Playback begins with the player’s play()
method
is called:
player.play()
Standard controls for controlling playback are provided by these methods:
Method Description play()
Begin or resume playback of the current source. pause()
Pause playback of the current source. next_source()
Dequeue the current source and move to the next one immediately. seek()
Seek to a specific time within the current source.
Note that there is no stop method. If you do not need to resume playback,
simply pause playback and discard the player and source objects. Using the
next_source()
method does not guarantee gapless
playback.
There are several properties that describe the player’s current state:
Property Description time
The current playback position within the current source, in seconds. This is read-only (but see the seek()
method).playing
True if the player is currently playing, False if there are no sources queued or the player is paused. This is read-only (but see the pause()
andplay()
methods).source
A reference to the current source being played. This is read-only (but see the queue()
method).volume
The audio level, expressed as a float from 0 (mute) to 1 (normal volume). This can be set at any time. loop
True
if the current source should be repeated when reaching the end. If set toFalse
, playback will continue to the next queued source.
When a player reaches the end of the current source, by default it will move
immediately to the next queued source. If there are no more sources, playback
stops until another source is queued. The Player
has a loop
attribute which determines
the player behaviour when the current source reaches the end. If
loop
is False
(default) the
Player
starts to play the next queued source.
Otherwise the Player
re-plays the current source
until either loop
is set to False
or next_source()
is called.
You can change the loop
attribute at
any time, but be aware that unless sufficient time is given for the future
data to be decoded and buffered there may be a stutter or gap in playback.
If set well in advance of the end of the source (say, several seconds), there
will be no disruption.
Gapless playback¶
To play back multiple similar sources without any audible gaps,
SourceGroup
is provided.
A SourceGroup
can only contain media sources
with identical audio or video format. First create an instance of
SourceGroup
, and then add all desired additional
sources with the add()
method.
Afterwards, you can queue the SourceGroup
on a Player as if it was a single source.
Incorporating video¶
When a Player
is playing back a source with
video, use the texture
property to obtain the
video frame image. This can be used to display the current video image
syncronised with the audio track, for example:
@window.event
def on_draw():
player.texture.blit(0, 0)
The texture is an instance of pyglet.image.Texture
, with an internal
format of either GL_TEXTURE_2D
or GL_TEXTURE_RECTANGLE_ARB
. While the
texture will typically be created only once and subsequentally updated each
frame, you should make no such assumption in your application – future
versions of pyglet may use multiple texture objects.
Positional audio¶
pyglet includes features for positioning sound within a 3D space. This is particularly effective with a surround-sound setup, but is also applicable to stereo systems.
A Player
in pyglet has an associated position
in 3D space – that is, it is equivalent to an OpenAL “source”. The properties
for setting these parameters are described in more detail in the API
documentation; see for example position
and
pitch
.
A “listener” object is provided by the audio driver. To obtain the listener for the current audio driver:
pyglet.media.get_audio_driver().get_listener()
This provides similar properties such as
position
,
forward_orientation
and
up_orientation
that
describe the position of the user in 3D space.
Note that only mono sounds can be positioned. Stereo sounds will play back as normal, and only their volume and pitch properties will affect the sound.
Ticking the clock¶
If you are using pyglet’s media libraries outside of a pyglet app, you will need to use some kind of loop to tick the pyglet clock periodically (perhaps every 200ms or so), otherwise only the first small sample of media will be played:
pyglet.clock.tick()
If you wish to have a media source loop continuously (player.loop = True) you will also need to ensure Pyglet’s events are dispatched inside your loop:
pyglet.app.platform_event_loop.dispatch_posted_events()
If you are inside a pyglet app then calling pyglet.app.run() takes care of all this for you.