LiTr (pronounced "lai-tr") is a lightweight video/audio transformation tool which supports transcoding video and audio tracks with optional frame modification.
In its current iteration LiTr supports:
By default, LiTr uses Android MediaCodec stack for hardware accelerated decoding/encoding and OpenGL for rendering. It also uses MediaExtractor and MediaMuxer to read/write media.
Simply grab via Gradle:
implementation 'com.linkedin.android.litr:litr:1.3.1'
...or Maven:
<dependency>
<groupId>com.linkedin.android.litr</groupId>
<artifactId>litr</artifactId>
<version>1.3.1</version>
</dependency>
First, instantiate MediaTransformer
with a Context
that can access Uri
s you will be using for input and output. Most commonly, that will be an application context.
MediaTransformer mediaTransformer = new MediaTransformer(getApplicationContext());
Then simply call transform
method to transform your video:
mediaTransformer.transform(requestId,
sourceVideoUri,
targetVideoFilePath,
targetVideoFormat,
targetAudioFormat,
videoTransformationListener,
MediaTransformer.GRANULARITY_DEFAULT,
glFilters);
Few notable things related to transformation:
requestId
, it will be used when calling back on a listener, or needed when cancelling an ongoing transformationnull
target format means that you don't want to modify track(s) of that typeGlFilter
s, which will be applied in ordertransform
multiple times, to queue transformation requestsprogress update granularity is 100 by default, to match percentage
Ongoing transformation can be cancelled by calling cancel
with its requestId
:
mediaTransformer.cancel(requestId);
When you no longer need MediaTransformer
, please release it. Note that MediaTransformer
instance becomes unusable after you release it, you will have to instantiate a new one.
mediaTransformer.release();
When transformation fails, exception is not thrown, but rather provided in TransformationListener.onError
callback. LiTr defines its own exceptions for different scenarios. For API >= 23, LiTr exception will also contain MediaCodec.CodecException
as a cause.
When possible, transformation statistics will be provided in listener callbacks. Statistics include source and target track formats, codecs used and transformation result and time for each track.
By default, LiTr uses Android MediaCodec stack to do all media work, and OpenGl for rendering. But this is not set in stone.
At high level, LiTr breaks down transformation into five essential steps:
Each transformation step is performed by a component. Each component is abstracted as an interface:
MediaSource
Decoder
Renderer
Encoder
MediaTarget
This allows clients pass in their own implementations of different transformation steps using more "low level" transform
API:
transform(requestId,
mediaSource,
decoder,
videoRenderer,
encoder,
mediaTarget,
targetVideoFormat,
targetAudioFormat,
listener,
granularity)
When using your own component implementations, make sure that output of a component matches the expected input of a next component. For example, if you are using a custom Encoder
(AV1?), make sure it accepts whatever frame format Renderer
produces (GlSurface
, ByteBuffer
) and outputs what MediaTarget
expects as an input.
Another way to gain even finer control over transformation is to use "track transformation" API:
tranform(requestId,
List<TrackTransform> trackTransforms,
listener,
granularity)
This API allows defining components and parameters per media track, thus allowing track based operations, such as muxing/demuxing tracks, transcoding different tracks differently, changing track order, etc.
You can use custom filters to modify video frames. Write your own in OpenGL as an implementation of GlFilter
interface when you need to make extra draw operations which do not need access to source video frames. If you need to change how source video frame is rendered onto a target video frame, implement GlFrameRender
interface. There are several filters already available from "filter pack" library, which is available via Gradle:
implementation 'com.linkedin.android.litr:litr-filters:1.3.1'
...or Maven:
<dependency>
<groupId>com.linkedin.android.litr</groupId>
<artifactId>litr-filters</artifactId>
<version>1.3.1</version>
</dependency>
You can pass in a list of filters when transforming a video. Keep in mind that filters will be applied in the order they are in the list, so ordering matters.
MediaTransformer
is very intentionally not a singleton, to allow easy mocking of it in unit tests. There is also MockMediaTransformer
for UI tests, which can synchronously "play back" a sequence of listener callbacks.
Core business logic in LiTr is well covered by unit tests. LiTr is designed to use dependency injection pattern, which makes it very easy to write JVM tests with mocked dependencies. We use Mockito framework for mocking.
LiTr comes with pretty useful demo app, which lets you transcode video/audio tracks with different parameters, in addition to providing sample code.
Please read CONTRIBUTING.md for details on our code of conduct, and the process for submitting pull requests to us.
For the versions available, see the tags on this repository.
See also the list of contributors who participated in this project.
This project is licensed under the BSD 2-Clause License - see the LICENSE file for details