关于FFMPeg-PHP你必须要知道的

 #PHP FFmpeg

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 An Object Oriented library to convert video/audio files with FFmpeg / AVConv.

 Check another amazing repo : [PHP FFMpeg extras](https://github.com/alchemy-fr/PHP-FFMpeg-Extras), you will find lots of Audio/Video formats there.

 ## Your attention please

 ### How this library works :

 This library requires a working FFMpeg install. You will need both FFMpeg and FFProbe binaries to use it.
 Be sure that these binaries can be located with system PATH to get the benefit of the binary detection,
 otherwise you should have to explicitely give the binaries path on load.

 For Windows users : Please find the binaries at http://ffmpeg.zeranoe.com/builds/.

 ### Known issues :

 - Using rotate and resize will produce a corrupted output when using
 [libav](http://libav.org/) 0.8. The bug is fixed in version 9. This bug does not
 appear in latest ffmpeg version.

 ## Installation

 The recommended way to install PHP-FFMpeg is through [Composer](https://getcomposer.org).

 ```json
 {
     "require": {
         "php-ffmpeg/php-ffmpeg": "~0.5"
     }
 }
 ```

 ## Basic Usage

 ```php
 $ffmpeg = FFMpeg\FFMpeg::create();
 $video = $ffmpeg->open('video.mpg');
 $video
     ->filters()
     ->resize(new FFMpeg\Coordinate\Dimension(320, 240))
     ->synchronize();
 $video
     ->frame(FFMpeg\Coordinate\TimeCode::fromSeconds(10))
     ->save('frame.jpg');
 $video
     ->save(new FFMpeg\Format\Video\X264(), 'export-x264.mp4')
     ->save(new FFMpeg\Format\Video\WMV(), 'export-wmv.wmv')
     ->save(new FFMpeg\Format\Video\WebM(), 'export-webm.webm');
 ```

 ## Documentation

 This documentation is an introduction to discover the API. It's recommended
 to browse the source code as it is self-documented.

 ### FFMpeg

 `FFMpeg\FFMpeg` is the main object to use to manipulate medias. To build it,
 use the static `FFMpeg\FFMpeg::create` :

 ```php
 $ffmpeg = FFMpeg\FFMpeg::create();
 ```

 FFMpeg will autodetect ffmpeg and ffprobe binaries. If you want to give binary
 paths explicitely, you can pass an array as configuration. A `Psr\Logger\LoggerInterface`
 can also be passed to log binary executions.

 ```php
 $ffmpeg = FFMpeg\FFMpeg::create(array(
     'ffmpeg.binaries'  => '/opt/local/ffmpeg/bin/ffmpeg',
     'ffprobe.binaries' => '/opt/local/ffmpeg/bin/ffprobe',
     'timeout'          => 3600, // The timeout for the underlying process
     'ffmpeg.threads'   => 12,   // The number of threads that FFMpeg should use
 ), $logger);
 ```

 ### Manipulate media

 `FFMpeg\FFMpeg` creates media based on URIs. URIs could be either a pointer to a
 local filesystem resource, an HTTP resource or any resource supported by FFmpeg.

 **Note** : To list all supported resource type of your FFmpeg build, use the
 `-protocols` command :

 ```
 ffmpeg -protocols
 ```

 To open a resource, use the `FFMpeg\FFMpeg::open` method.

 ```php
 $ffmpeg->open('video.mpeg');
 ```

 Two types of media can be resolved : `FFMpeg\Media\Audio` and `FFMpeg\Media\Video`.
 A third type, `FFMpeg\Media\Frame`, is available through videos.

 #### Video

 `FFMpeg\Media\Video` can be transcoded, ie : change codec, isolate audio or
 video. Frames can be extracted.

 ##### Transcoding

 You can transcode videos using the `FFMpeg\Media\Video:save` method. You will
 pass a `FFMpeg\Format\FormatInterface` for that.

 Please note that audio and video bitrate are set on the format.

 ```php
 $format = new Format\Video\X264();
 $format->on('progress', function ($video, $format, $percentage) {
     echo "$percentage % transcoded";
 });

 $format
     -> setKiloBitrate(1000)
     -> setAudioChannels(2)
     -> setAudioKiloBitrate(256);

 $video->save($format, 'video.avi');
 ```

 Transcoding progress can be monitored in realtime, see Format documentation
 below for more informations.

 ##### Extracting image

 You can extract a frame at any timecode using the `FFMpeg\Media\Video::frame`
 method.

 This code return a `FFMpeg\Media\Frame` instance corresponding to the second 42.
 You can pass any `FFMpeg\Coordinate\TimeCode` as argument, see dedicated
 documentation below for more information.

 ```php
 $frame = $video->frame(FFMpeg\Coordinate\TimeCode::fromSeconds(42));
 $frame->save('image.jpg');
 ```

 ##### Filters

 You can apply filters on `FFMpeg\Media\Video` with the `FFMpeg\Media\Video::addFilter`
 method. Video accepts Audio and Video filters.

 You can build your own filters and some are bundled in PHP-FFMpeg - they are
 accessible through the `FFMpeg\Media\Video::filters` method.

 Filters are chainable

 ```php
 $video
     ->filters()
     ->resize($dimension, $mode, $useStandards)
     ->framerate($framerate, $gop)
     ->synchronize();
 ```

 ###### Rotate

 Rotates a video to a given angle.

 ```php
 $video->filters()->rotate($angle);
 ```

 The `$angle` parameter must be one of the following constants :

 - `FFMpeg\Filters\Video\RotateFilter::ROTATE_90` : 90° clockwise
 - `FFMpeg\Filters\Video\RotateFilter::ROTATE_180` : 180°
 - `FFMpeg\Filters\Video\RotateFilter::ROTATE_270` : 90° counterclockwise

 ###### Resize

 Resizes a video to a given size.

 ```php
 $video->filters()->resize($dimension, $mode, $useStandards);
 ```

 The resize filter takes three parameters :

 - `$dimension`, an instance of `FFMpeg\Coordinate\Dimension`
 - `$mode`, one of the constants `FFMpeg\Filters\Video\ResizeFilter::RESIZEMODE_*` constants
 - `$useStandards`, a boolean to force the use of the nearest aspect ratio standard.

 ###### Watermark

 Watermark a video with a given image.

 ```php
 $video
     ->filters()
     ->watermark($watermarkPath, array(
         'position' => 'relative',
         'bottom' => 50,
         'right' => 50,
     ));
 ```

 The watermark filter takes two parameters:

 `$watermarkPath`, the path to your watermark file.
 `$coordinates`, an array defining how you want your watermark positioned. You can use relative positioning as demonstrated above or absolute as such:

 ```php
 $video
     ->filters()
     ->watermark($watermarkPath, array(
         'position' => 'absolute',
         'x' => 1180,
         'y' => 620,
     ));
 ```

 ###### Framerate

 Changes the frame rate of the video.

 ```php
 $video->filters()->framerate($framerate, $gop);
 ```

 The framerate filter takes two parameters :

 - `$framerate`, an instance of `FFMpeg\Coordinate\Framerate`
 - `$gop`, a [GOP](https://wikipedia.org/wiki/Group_of_pictures) value (integer)

 ###### Synchronize

 Synchronizes audio and video.

 Some containers may use a delay that results in desynchronized outputs. This
 filters solves this issue.

 ```php
 $video->filters()->synchronize();
 ```

 ###### Clip

 Cuts the video at a desired point.

 ```php
 $video->filters()->clip(FFMpeg\Coordinate\TimeCode::fromSeconds(30), FFMpeg\Coordinate\TimeCode::fromSeconds(15));
 ```

 The clip filter takes two parameters:

 - `$start`, an instance of `FFMpeg\Coordinate\TimeCode`, specifies the start point of the clip
 - `$duration`, optional, an instance of `FFMpeg\Coordinate\TimeCode`, specifies the duration of the clip

 #### Audio

 `FFMpeg\Media\Audio` can be transcoded, ie : change codec, isolate audio or
 video. Frames can be extracted.

 ##### Transcoding

 You can transcode audios using the `FFMpeg\Media\Audio:save` method. You will
 pass a `FFMpeg\Format\FormatInterface` for that.

 Please note that audio kilobitrate is set on the audio format.

 ```php
 $ffmpeg = FFMpeg\FFMpeg::create();
 $audio = $ffmpeg->open('track.mp3');

 $format = new FFMpeg\Format\Audio\Flac();
 $format->on('progress', function ($audio, $format, $percentage) {
     echo "$percentage % transcoded";
 });

 $format
     -> setAudioChannels(2)
     -> setAudioKiloBitrate(256);

 $audio->save($format, 'track.flac');
 ```

 Transcoding progress can be monitored in realtime, see Format documentation
 below for more informations.

 ##### Filters

 You can apply filters on `FFMpeg\Media\Audio` with the `FFMpeg\Media\Audio::addFilter`
 method. It only accepts audio filters.

 You can build your own filters and some are bundled in PHP-FFMpeg - they are
 accessible through the `FFMpeg\Media\Audio::filters` method.

 ###### Resample

 Resamples an audio file.

 ```php
 $audio->filters()->resample($rate);
 ```

 The resample filter takes two parameters :

 - `$rate`, a valid audio sample rate value (integer)

 #### Frame

 A frame is a image at a timecode of a video ; see documentation above about
 frame extraction.

 You can save frames using the `FFMpeg\Media\Frame::save` method.

 ```php
 $frame->save('target.jpg');
 ```

 This method has a second optional boolean parameter. Set it to true to get
 accurate images ; it takes more time to execute.

 #### Formats

 A format implements `FFMpeg\Format\FormatInterface`. To save to a video file,
 use `FFMpeg\Format\VideoInterface`, and `FFMpeg\Format\AudioInterface` for
 audio files.

 Format can also extends `FFMpeg\Format\ProgressableInterface` to get realtime
 informations about the transcoding.

 Predefined formats already provide progress informations as events.

 ```php
 $format = new Format\Video\X264();
 $format->on('progress', function ($video, $format, $percentage) {
     echo "$percentage % transcoded";
 });

 $video->save($format, 'video.avi');
 ```

 The callback provided for the event can be any callable.

 ##### Create your own format

 The easiest way to create a format is to extend the abstract
 `FFMpeg\Format\Video\DefaultVideo` and `FFMpeg\Format\Audio\DefaultAudio`.
 and implement the following methods.

 ```php
 class CustomWMVFormat extends FFMpeg\Format\Video\DefaultVideo
 {
     public function __construct($audioCodec = 'wmav2', $videoCodec = 'wmv2')
     {
         $this
             ->setAudioCodec($audioCodec)
             ->setVideoCodec($videoCodec);
     }

     public function supportBFrames()
     {
         return false;
     }

     public function getAvailableAudioCodecs()
     {
         return array('wmav2');
     }

     public function getAvailableVideoCodecs()
     {
         return array('wmv2');
     }
 }
 ```

 #### Coordinates

 FFMpeg use many units for time and space coordinates.

 - `FFMpeg\Coordinate\AspectRatio` represents an aspect ratio.
 - `FFMpeg\Coordinate\Dimension` represent a dimension.
 - `FFMpeg\Coordinate\FrameRate` represent a framerate.
 - `FFMpeg\Coordinate\Point` represent a point.
 - `FFMpeg\Coordinate\TimeCode` represent a timecode.

 ### FFProbe

 `FFMpeg\FFProbe` is used internally by `FFMpeg\FFMpeg` to probe medias. You can
 also use it to extract media metadata.

 ```php
 $ffprobe = FFMpeg\FFProbe::create();
 $ffprobe
     ->streams('/path/to/video/mp4') // extracts streams informations
     ->videos()                      // filters video streams
     ->first()                       // returns the first video stream
     ->get('codec_name');            // returns the codec_name property
 ```

 ```php
 $ffprobe = FFMpeg\FFProbe::create();
 $ffprobe
     ->format('/path/to/video/mp4') // extracts file informations
     ->get('duration');             // returns the duration property
 ```

 ##Using with Silex Microframework

 Service provider is easy to set up :

 ```php
 $app = new Silex\Application();
 $app->register(new FFMpeg\FFMpegServiceProvider());

 $video = $app['ffmpeg']->open('video.mpeg');
 ```

 Available options are as follow :

 ```php
 $app->register(new FFMpeg\FFMpegServiceProvider(), array(
     'ffmpeg.configuration' => array(
         'ffmpeg.threads'   => 4,
         'ffmpeg.timeout'   => 300,
         'ffmpeg.binaries'  => '/opt/local/ffmpeg/bin/ffmpeg',
         'ffprobe.timeout'  => 30,
         'ffprobe.binaries' => '/opt/local/ffmpeg/bin/ffprobe',
     ),
     'ffmpeg.logger' => $logger,
 ));
 ```

 ## API Browser

 Browse the [API](http://readthedocs.org/docs/ffmpeg-php/en/latest/_static/API/)

 ## License

 This project is licensed under the [MIT license](http://opensource.org/licenses/MIT).