Function avcodec_open2

pub unsafe extern "C" fn avcodec_open2(
    avctx: *mut AVCodecContext,
    codec: *const AVCodec,
    options: *mut *mut AVDictionary,
) -> i32

Initialize the AVCodecContext to use the given AVCodec. Prior to using this function the context has to be allocated with avcodec_alloc_context3().

The functions avcodec_find_decoder_by_name(), avcodec_find_encoder_by_name(), avcodec_find_decoder() and avcodec_find_encoder() provide an easy way for retrieving a codec.

Depending on the codec, you might need to set options in the codec context also for decoding (e.g. width, height, or the pixel or audio sample format in the case the information is not available in the bitstream, as when decoding raw audio or video).

Options in the codec context can be set either by setting them in the options AVDictionary, or by setting the values in the context itself, directly or by using the av_opt_set() API before calling this function.

Example: @code av_dict_set(&opts, “b”, “2.5M”, 0); codec = avcodec_find_decoder(AV_CODEC_ID_H264); if (!codec) exit(1);

context = avcodec_alloc_context3(codec);

if (avcodec_open2(context, codec, opts) < 0) exit(1); @endcode

In the case AVCodecParameters are available (e.g. when demuxing a stream using libavformat, and accessing the AVStream contained in the demuxer), the codec parameters can be copied to the codec context using avcodec_parameters_to_context(), as in the following example:

@code AVStream *stream = …; context = avcodec_alloc_context3(codec); if (avcodec_parameters_to_context(context, stream->codecpar) < 0) exit(1); if (avcodec_open2(context, codec, NULL) < 0) exit(1); @endcode

@note Always call this function before using decoding routines (such as @ref avcodec_receive_frame()).

@param avctx The context to initialize. @param codec The codec to open this context for. If a non-NULL codec has been previously passed to avcodec_alloc_context3() or for this context, then this parameter MUST be either NULL or equal to the previously passed codec. @param options A dictionary filled with AVCodecContext and codec-private options, which are set on top of the options already set in avctx, can be NULL. On return this object will be filled with options that were not found in the avctx codec context.

@return zero on success, a negative value on error @see avcodec_alloc_context3(), avcodec_find_decoder(), avcodec_find_encoder(), av_dict_set(), av_opt_set(), av_opt_find(), avcodec_parameters_to_context()