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diff --git a/doc/src/audiooverview.qdoc b/doc/src/audiooverview.qdoc index 6f774b519..d9872ffcc 100644 --- a/doc/src/audiooverview.qdoc +++ b/doc/src/audiooverview.qdoc @@ -28,12 +28,15 @@ /*! \page audiooverview.html \title Audio Overview -\brief Audio playback and recording +\brief Audio playback, recording and processing \section1 Audio Features Qt Multimedia offers a range of audio classes, covering both low and -high level approaches to audio input and output. +high level approaches to audio input, output and processing. In +addition to traditional audio usage, the \l {QtAudioEngine}{Qt AudioEngine} +QML classes offers high level 3D positional audio for QML applications. +See that documentation for more information. \section1 Audio Implementation Details @@ -51,7 +54,16 @@ or VOIP) and high latency (like music playback). The available hardware determines what audio outputs and inputs are available. \section3 Push and Pull -[TBD] - description of push vs. pull mode. +The low level audio classes can operate in two modes - \c push and \c pull. +In \c pull mode, the audio device is started by giving it a QIODevice. For +an output device, the QAudioOutput class will pull data from the QIODevice +(using \l QIODevice::read()) when more audio data is required. Conversely, +for \c pull mode with QAudioInput, when audio data is available then the +data will be written directly to the QIODevice. + +In \c push mode, the audio device provides a QIODevice instance that +can be written or read to as needed. Typically this results in simpler +code but more buffering, which may affect latency. \section2 Low latency sound effects @@ -82,12 +94,43 @@ Here is how you play a local file using C++: You can also put files (even remote URLs) into a playlist: \snippet doc/src/snippets/multimedia-snippets/media.cpp Audio playlist +\section2 Decoding compressed audio to memory +In some cases you may want to decode a compressed audio file and do further +processing yourself (like mix multiple samples, or some custom digital signal +processing algorithms). Qt Multimedia 5.0 offers a preliminary API for this +case - the \l QAudioDecoder class. QAudioDecoder supports decoding local files +or from a QIODevice instances. + +Here's an example of decoding a local file: + + \snippet doc/src/snippets/multimedia-snippets/audio.cpp Local audio decoding + +Note: This API is preliminary at this time - the API may change or be +removed before the final 5.0 release. In addition, it is necessary to +add "multimedia-private" to the QT variable in your .pro file to use this class. + + \snippet doc/src/snippets/multimedia-snippets/audio.cpp Audio decoder header + \section2 Recording audio to a file For recording audio to a file, the \l {QAudioRecorder} class allows you to compress audio data from an input device and record it. \snippet doc/src/snippets/multimedia-snippets/media.cpp Audio recorder +\section2 Monitoring audio data during playback or recording + +The \l QAudioProbe class allows you to monitor audio data being played or +recorded in the higher level classes like \l QMediaPlayer, \l QCamera and +\l QAudioRecorder. After creating your high level class, you can simply +set the source of the probe to your class, and receive audio buffers as they +are processed. This is useful for several audio processing tasks, particularly +for visualization or adjusting gain. You cannot modify the buffers, and +they may arrive at a slightly different time than the media pipeline +processes them. + +Here's an example of installing a probe during recording: + \snippet doc/src/snippets/multimedia-snippets/media.cpp Audio probe + \section1 Examples There are both C++ and QML examples available. |