Buffer sink API

The buffersink and abuffersink filters are there to connect filter graphs to applications. More...

Modules
	Buffer sink accessors
	Get the properties of the stream.

Files
file	buffersink.h
	memory buffer sink API for audio and video

Macros
#define	AV_BUFFERSINK_FLAG_PEEK   1
	Tell av_buffersink_get_buffer_ref() to read video/samples buffer reference, but not remove it from the buffer. More...
#define	AV_BUFFERSINK_FLAG_NO_REQUEST   2
	Tell av_buffersink_get_buffer_ref() not to request a frame from its input. More...

Functions
int	av_buffersink_get_frame_flags (AVFilterContext *ctx, AVFrame *frame, int flags)
	Get a frame with filtered data from sink and put it in frame. More...
void	av_buffersink_set_frame_size (AVFilterContext *ctx, unsigned frame_size)
	Set the frame size for an audio buffer sink. More...
int	av_buffersink_get_frame (AVFilterContext *ctx, AVFrame *frame)
	Get a frame with filtered data from sink and put it in frame. More...
int	av_buffersink_get_samples (AVFilterContext *ctx, AVFrame *frame, int nb_samples)
	Same as av_buffersink_get_frame(), but with the ability to specify the number of samples read. More...

Detailed Description

The buffersink and abuffersink filters are there to connect filter graphs to applications.

They have a single input, connected to the graph, and no output. Frames must be extracted using av_buffersink_get_frame() or av_buffersink_get_samples().

The format negotiated by the graph during configuration can be obtained using the accessor functions:

• av_buffersink_get_time_base(),
• av_buffersink_get_format(),
• av_buffersink_get_frame_rate(),
• av_buffersink_get_w(),
• av_buffersink_get_h(),
• av_buffersink_get_sample_aspect_ratio(),
• av_buffersink_get_channels(),
• av_buffersink_get_ch_layout(),
• av_buffersink_get_sample_rate().

The layout returned by av_buffersink_get_ch_layout() must de uninitialized by the caller.

The format can be constrained by setting options, using av_opt_set() and related functions with the AV_OPT_SEARCH_CHILDREN flag.

• pix_fmts (int list),
• sample_fmts (int list),
• sample_rates (int list),
• ch_layouts (string),
• channel_counts (int list),
• all_channel_counts (bool). Most of these options are of type binary, and should be set using av_opt_set_int_list() or av_opt_set_bin(). If they are not set, all corresponding formats are accepted.

As a special case, if ch_layouts is not set, all valid channel layouts are accepted except for UNSPEC layouts, unless all_channel_counts is set.

Macro Definition Documentation

AV_BUFFERSINK_FLAG_PEEK

#define AV_BUFFERSINK_FLAG_PEEK   1

Tell av_buffersink_get_buffer_ref() to read video/samples buffer reference, but not remove it from the buffer.

This is useful if you need only to read a video/samples buffer, without to fetch it.

Definition at line 88 of file buffersink.h.

AV_BUFFERSINK_FLAG_NO_REQUEST

#define AV_BUFFERSINK_FLAG_NO_REQUEST   2

Tell av_buffersink_get_buffer_ref() not to request a frame from its input.

If a frame is already buffered, it is read (and removed from the buffer), but if no frame is present, return AVERROR(EAGAIN).

Definition at line 95 of file buffersink.h.

Function Documentation

av_buffersink_get_frame_flags()

int av_buffersink_get_frame_flags	(	AVFilterContext *	ctx,
		AVFrame *	frame,
		int	flags
	)

Get a frame with filtered data from sink and put it in frame.

Parameters

ctx	pointer to a buffersink or abuffersink filter context.
frame	pointer to an allocated frame that will be filled with data. The data must be freed using av_frame_unref() / av_frame_free()
flags	a combination of AV_BUFFERSINK_FLAG_* flags

Returns

>= 0 in for success, a negative AVERROR code for failure.

av_buffersink_set_frame_size()

void av_buffersink_set_frame_size	(	AVFilterContext *	ctx,
		unsigned	frame_size
	)

Set the frame size for an audio buffer sink.

All calls to av_buffersink_get_buffer_ref will return a buffer with exactly the specified number of samples, or AVERROR(EAGAIN) if there is not enough. The last buffer at EOF will be padded with 0.

av_buffersink_get_frame()

int av_buffersink_get_frame	(	AVFilterContext *	ctx,
		AVFrame *	frame
	)

Get a frame with filtered data from sink and put it in frame.

Parameters

ctx	pointer to a context of a buffersink or abuffersink AVFilter.
frame	pointer to an allocated frame that will be filled with data. The data must be freed using av_frame_unref() / av_frame_free()

Returns

• >= 0 if a frame was successfully returned.
• AVERROR(EAGAIN) if no frames are available at this point; more input frames must be added to the filtergraph to get more output.
• AVERROR_EOF if there will be no more output frames on this sink.
• A different negative AVERROR code in other failure cases.

Examples

filter_audio.c, filtering_audio.c, filtering_video.c, and transcoding.c.

Referenced by filter_encode_write_frame(), and main().

av_buffersink_get_samples()

int av_buffersink_get_samples	(	AVFilterContext *	ctx,
		AVFrame *	frame,
		int	nb_samples
	)

Same as av_buffersink_get_frame(), but with the ability to specify the number of samples read.

This function is less efficient than av_buffersink_get_frame(), because it copies the data around.

Parameters

ctx	pointer to a context of the abuffersink AVFilter.
frame	pointer to an allocated frame that will be filled with data. The data must be freed using av_frame_unref() / av_frame_free() frame will contain exactly nb_samples audio samples, except at the end of stream, when it can contain less than nb_samples.

Returns

The return codes have the same meaning as for av_buffersink_get_frame().

Warning

do not mix this function with av_buffersink_get_frame(). Use only one or the other with a single sink, not both.