libvideo-decode is a C library to handle the decoding of H.264 video on various platforms with a common API.
The library uses hardware-accelerated decoding when available.
The following implementations are available:
- FFmpeg (CPU or cuvid acceleration on Nvidia GPU if available)
- MediaCodec on Android 4.2+ (through the NDK API on Android 5.0+ or the Java API through JNI)
- VideoToolbox on iOS 8+ and MacOS X
- MMAL on Broadcom VideoCore IV (Raspberry Pi platforms)
The application can force using a specific implementation or let the library decide according to what is supported by the platform.
The library depends on the following Alchemy modules:
- libulog
- libfutils
- libvideo-buffers
- libh264
- (optional) ffmpeg-libav (for FFmpeg support)
- (optional) libvideo-buffers-generic (for FFmpeg support)
- (optional) mmal (for Broadcom VideoCore IV)
The library also depends on the following frameworks for iOS and MacOS only:
- Foundation
- CoreMedia
- CoreVideo
- VideoToolbox
Building is activated by enabling libvideo-decode in the Alchemy build configuration.
Operations are asynchronous: the application pushes buffers to decode in the input queue and is notified of decoded frames through a callback function.
Some decoders need the input buffers to be originating from its own buffer pool; when the input buffer pool returned by the library is not NULL it must be used and input buffers cannot be shared with other video pipeline elements.
The library is designed to run on a libpomp event loop (pomp_loop, see libpomp documentation). All API functions must be called from the pomp_loop thread. All callback functions (frame_output, flush or stop) are called from the pomp_loop thread.
The library can be tested using the provided vdec command-line tool which takes as input a raw H.264 (annex B byte stream) file and can optionally output a decoded YUV file.
To build the tool, enable vdec in the Alchemy build configuration.
For a list of available options, run
$ vdec -h