Codec.FFmpeg.Encode

Video encoding API. Includes FFI declarations for the underlying FFmpeg functions, wrappers for these functions that wrap error condition checking, and high level Haskellized interfaces.

Note: If you need to import this module, consider qualifying the import.

FFI Declarations

avcodec_find_encoder :: AVCodecID -> IO AVCodec

avcodec_find_encoder_by_name :: CString -> IO AVCodec

av_opt_set :: Ptr () -> CString -> CString -> CInt -> IO CInt

avcodec_encode_video2 :: AVCodecContext -> AVPacket -> AVFrame -> Ptr CInt -> IO CInt

av_image_alloc :: Ptr (Ptr CUChar) -> Ptr CInt -> CInt -> CInt -> AVPixelFormat -> CInt -> IO CInt

av_freep :: Ptr (Ptr a) -> IO ()

av_guess_format :: CString -> CString -> CString -> IO AVOutputFormat

avformat_alloc_output_context :: Ptr AVFormatContext -> AVOutputFormat -> CString -> CString -> IO CInt

avformat_new_stream :: AVFormatContext -> AVCodec -> IO AVStream

av_write_frame :: AVFormatContext -> AVPacket -> IO CInt

av_interleaved_write_frame :: AVFormatContext -> AVPacket -> IO CInt

avformat_write_header :: AVFormatContext -> Ptr AVDictionary -> IO CInt

av_write_trailer :: AVFormatContext -> IO CInt

avio_open :: Ptr AVIOContext -> CString -> AVIOFlag -> IO CInt

avio_close :: AVIOContext -> IO CInt

avformat_free_context :: AVFormatContext -> IO ()

av_image_fill_arrays :: Ptr (Ptr CUChar) -> Ptr CInt -> Ptr CUChar -> AVPixelFormat -> CInt -> CInt -> CInt -> IO CInt

av_image_fill_linesizes :: Ptr CInt -> AVPixelFormat -> CInt -> IO CInt

FFmpeg Encoding Interface

data EncodingParams

Minimal parameters describing the desired video output.

Constructors

EncodingParams

Fields

• epWidth :: CInt
• epHeight :: CInt
• epFps :: Int
• epCodec :: Maybe AVCodecID

  If Nothing, then the codec is inferred from the output file name. If Just, then this codec is manually chosen.

• epPixelFormat :: Maybe AVPixelFormat

  If Nothing, automatically chose a pixel format based on the output codec. If Just, force the selected pixel format.

• epPreset :: String

  Encoder-specific hints. For h264, the default preset is "medium" (other options are "fast", "slow", etc.). For the GIF codec, setting this to "dither" will enable dithering during the palettization process. This will improve image quality, but result in a larger file.

defaultH264 :: CInt -> CInt -> EncodingParams

Use default parameters for a video of the given width and height, forcing the choice of the h264 encoder.

defaultParams :: CInt -> CInt -> EncodingParams

Use default parameters for a video of the given width and height. The output format is determined by the output file name.

checkFlag :: Bits a => a -> a -> Bool

Determine if the bitwise intersection of two values is non-zero.

initStream :: EncodingParams -> AVFormatContext -> IO (AVStream, AVCodecContext)

Find and initialize the requested encoder, and add a video stream to the output container.

initTempFrame :: EncodingParams -> AVPixelFormat -> IO AVFrame

Initialize a temporary YUV frame of the same resolution as the output video stream. We well convert RGB frames using this frame as a destination before encoding the video frame.

allocOutputContext :: FilePath -> IO AVFormatContext

Allocate an output context inferring the codec from the given file name.

avio_open_check :: AVFormatContext -> String -> IO ()

Open the given file for writing.

avio_close_check :: AVFormatContext -> IO ()

Close an open IO context.

encode_video_check :: AVCodecContext -> AVPacket -> Maybe AVFrame -> IO Bool

Returns True if the AVPacket was updated with new output data; False otherwise.

write_header_check :: AVFormatContext -> IO ()

Allocate the stream private data and write the stream header to an output media file.

write_frame_check :: AVFormatContext -> AVPacket -> IO ()

Write a packet to an output media file.

write_trailer_check :: AVFormatContext -> IO ()

Write the stream trailer to an output media file and free the private data. May only be called after a successful call to write_header_check.

palettizeRGB8 :: EncodingParams -> Vector CUChar -> Vector CUChar

Quantize RGB24 pixels to the systematic RGB8 color palette. The image data has space for a palette appended to be compliant with av_image_fill_arrays's expectations. This is slow.

palettizeJuicy :: EncodingParams -> Vector CUChar -> Vector CUChar

High quality dithered, median cut palette using palettize. The result is packed such that the BGRA palette is laid out contiguously following the palettized image data.

frameWriter :: EncodingParams -> FilePath -> IO (Maybe (AVPixelFormat, V2 CInt, Vector CUChar) -> IO ())

Open a target file for writing a video stream. The function returned may be used to write image frames (specified by a pixel format, resolution, and pixel data). If this function is applied to Nothing, then the output stream is closed. Note that Nothing must be provided to properly terminate video encoding.

Support for source images that are of a different size to the output resolution is limited to non-palettized destination formats (i.e. those that are handled by libswscaler). Practically, this means that animated gif output only works if the source images are of the target resolution.

frameWriterRgb :: EncodingParams -> FilePath -> IO (Maybe (Vector CUChar) -> IO ())

Open a target file for writing a video stream. The function returned may be used to write RGB images of the resolution given by the provided EncodingParams (i.e. the same resolution as the output video). If this function is applied to Nothing, then the output stream is closed. Note that Nothing must be provided to properly terminate video encoding.