Decoding
[Encoding/Decoding Library]

Modules
	Frame parsing
Defines
#define	FF_INPUT_BUFFER_PADDING_SIZE   16
	Required number of additionally allocated bytes at the end of the input bitstream for decoding.
Enumerations
enum	AVDiscard {   AVDISCARD_NONE = -16, AVDISCARD_DEFAULT = 0, AVDISCARD_NONREF = 8, AVDISCARD_BIDIR = 16,   AVDISCARD_NONKEY = 32, AVDISCARD_ALL = 48 }
Functions
AVCodec *	avcodec_find_decoder (enum CodecID id)
	Find a registered decoder with a matching codec ID.
AVCodec *	avcodec_find_decoder_by_name (const char *name)
	Find a registered decoder with the specified name.
int	avcodec_default_get_buffer (AVCodecContext *s, AVFrame *pic)
void	avcodec_default_release_buffer (AVCodecContext *s, AVFrame *pic)
int	avcodec_default_reget_buffer (AVCodecContext *s, AVFrame *pic)
unsigned	avcodec_get_edge_width (void)
	Return the amount of padding in pixels which the get_buffer callback must provide around the edge of the image for codecs which do not have the CODEC_FLAG_EMU_EDGE flag.
void	avcodec_align_dimensions (AVCodecContext *s, int *width, int *height)
	Modify width and height values so that they will result in a memory buffer that is acceptable for the codec if you do not use any horizontal padding.
void	avcodec_align_dimensions2 (AVCodecContext *s, int *width, int *height, int linesize_align[AV_NUM_DATA_POINTERS])
	Modify width and height values so that they will result in a memory buffer that is acceptable for the codec if you also ensure that all line sizes are a multiple of the respective linesize_align[i].
attribute_deprecated int	avcodec_decode_audio3 (AVCodecContext *avctx, int16_t *samples, int *frame_size_ptr, AVPacket *avpkt)
	Wrapper function which calls avcodec_decode_audio4.
int	avcodec_decode_audio4 (AVCodecContext *avctx, AVFrame *frame, int *got_frame_ptr, const AVPacket *avpkt)
	Decode the audio frame of size avpkt->size from avpkt->data into frame.
int	avcodec_decode_video2 (AVCodecContext *avctx, AVFrame *picture, int *got_picture_ptr, const AVPacket *avpkt)
	Decode the video frame of size avpkt->size from avpkt->data into picture.
int	avcodec_decode_subtitle2 (AVCodecContext *avctx, AVSubtitle *sub, int *got_sub_ptr, AVPacket *avpkt)
	Decode a subtitle message.

---

Define Documentation

#define FF_INPUT_BUFFER_PADDING_SIZE   16

Required number of additionally allocated bytes at the end of the input bitstream for decoding.

This is mainly needed because some optimized bitstream readers read 32 or 64 bit at once and could read over the end.
Note: If the first 23 bits of the additional bytes are not 0, then damaged MPEG bitstreams could cause overread and segfault.

Definition at line 458 of file avcodec.h.

Referenced by a64multi_init_encoder(), aac_adtstoasc_filter(), aac_decode_frame(), aac_encode_init(), aacPlus_encode_init(), adpcm_encode_init(), adx_read_header(), aiff_read_header(), alac_encode_init(), alloc_buffers(), apc_read_header(), ape_tag_read_field(), asf_read_stream_properties(), atrac3_decode_init(), audio_decode_example(), av_fast_padded_malloc(), av_grow_packet(), av_new_packet(), av_packet_merge_side_data(), av_packet_new_side_data(), av_packet_split_side_data(), av_parser_change(), av_parser_parse2(), av_shrink_packet(), avcodec_copy_context(), avcodec_encode_audio2(), avcodec_encode_video2(), avformat_find_stream_info(), avi_read_header(), avio_close_dyn_buf(), avisynth_read_header(), avui_encode_init(), cdxl_decode_frame(), celt_header(), cook_decode_init(), dca_parse_params(), decode_frame(), decode_i_frame(), decode_init(), decode_p_frame(), decode_plane(), decode_stream_header(), dshow_add_device(), dump_extradata(), dv_decode_video_segment(), encode_init(), extract_header(), Faac_encode_init(), ff_alloc_packet2(), ff_asf_parse_packet(), ff_combine_frame(), ff_h263_decode_frame(), ff_h264_decode_nal(), ff_mp4_read_dec_config_descr(), ff_mpeg_update_thread_context(), ff_parse_mpeg2_descriptor(), fixup_vorbis_headers(), flac_header(), flac_read_header(), flic_decode_frame_8BPP(), flv_get_extradata(), flv_queue_extradata(), flv_set_video_codec(), h264_mp4toannexb_filter(), h264_new_context(), handle_packets(), iff_read_header(), imx_dump_header(), jacosub_read_header(), latm_decode_audio_specific_config(), matroska_fix_ass_packet(), matroska_read_header(), mjpega_dump_header(), mov2textsub(), mov_read_dvc1(), mov_read_extradata(), mov_read_glbl(), mov_read_smi(), mov_read_strf(), mov_read_stsz(), mov_read_wave(), mov_write_dvc1_structs(), mp3_header_compress(), mp3_header_decompress(), mp_decode_frame(), mpc8_parse_seektable(), mpc8_read_header(), mpc_read_header(), mpegts_push_data(), mxf_read_generic_descriptor(), mxg_update_cache(), new_pes_packet(), noise(), ogg_new_buf(), ogg_new_stream(), ogg_read_page(), ogg_save(), oggvorbis_encode_init(), ogm_header(), oma_read_header(), parse_fmtp_config(), parse_packed_headers(), qdm2_parse_config(), qt_rtp_parse_packet(), rdt_parse_b64buf(), read_header(), read_kuki_chunk(), rl2_read_header(), rm_read_audio_stream_info(), rm_read_extradata(), sdp_parse_fmtp_config_h264(), smacker_read_header(), spdif_write_packet(), speex_header(), Stagefright_init(), submit_packet(), svq3_decode_frame(), svq3_parse_packet(), text2movsub(), theora_header(), tiff_unpack_strip(), transcode_init(), tta_read_header(), vc1_decode_frame(), vc1_decode_init(), vc1_extract_headers(), vfw_read_header(), video_decode_example(), vmd_read_header(), vqf_read_header(), wma_decode_superframe(), wsvqa_read_header(), wsvqa_read_packet(), wv_get_value_float(), xmv_process_packet_header(), xwma_read_header(), and yop_read_header().

---

Enumeration Type Documentation

enum AVDiscard

Enumerator:

AVDISCARD_NONE	discard nothing
AVDISCARD_DEFAULT	discard useless packets like 0 size packets in avi
AVDISCARD_NONREF	discard all non reference
AVDISCARD_BIDIR	discard all bidirectional frames
AVDISCARD_NONKEY	discard all frames except keyframes
AVDISCARD_ALL	discard all

Definition at line 488 of file avcodec.h.

---

Function Documentation

void avcodec_align_dimensions	(	AVCodecContext *	s,
		int *	width,
		int *	height
	)

Modify width and height values so that they will result in a memory buffer that is acceptable for the codec if you do not use any horizontal padding.

May only be used if a codec with CODEC_CAP_DR1 has been opened. If CODEC_FLAG_EMU_EDGE is not set, the dimensions must have been increased according to avcodec_get_edge_width() before.

Definition at line 251 of file utils.c.

Referenced by alloc_buffer().

void avcodec_align_dimensions2	(	AVCodecContext *	s,
		int *	width,
		int *	height,
		int	linesize_align[AV_NUM_DATA_POINTERS]
	)

Modify width and height values so that they will result in a memory buffer that is acceptable for the codec if you also ensure that all line sizes are a multiple of the respective linesize_align[i].

May only be used if a codec with CODEC_CAP_DR1 has been opened. If CODEC_FLAG_EMU_EDGE is not set, the dimensions must have been increased according to avcodec_get_edge_width() before.

Definition at line 158 of file utils.c.

Referenced by avcodec_align_dimensions(), and video_get_buffer().

attribute_deprecated int avcodec_decode_audio3	(	AVCodecContext *	avctx,
		int16_t *	samples,
		int *	frame_size_ptr,
		AVPacket *	avpkt
	)

Wrapper function which calls avcodec_decode_audio4.

Deprecated:

Use avcodec_decode_audio4 instead.

Decode the audio frame of size avpkt->size from avpkt->data into samples. Some decoders may support multiple frames in a single AVPacket, such decoders would then just decode the first frame. In this case, avcodec_decode_audio3 has to be called again with an AVPacket that contains the remaining data in order to decode the second frame etc. If no frame could be outputted, frame_size_ptr is zero. Otherwise, it is the decompressed frame size in bytes.

Warning:

You must set frame_size_ptr to the allocated size of the output buffer before calling avcodec_decode_audio3().

The input buffer must be FF_INPUT_BUFFER_PADDING_SIZE larger than the actual read bytes because some optimized bitstream readers read 32 or 64 bits at once and could read over the end.

The end of the input buffer avpkt->data should be set to 0 to ensure that no overreading happens for damaged MPEG streams.

You must not provide a custom get_buffer() when using avcodec_decode_audio3(). Doing so will override it with avcodec_default_get_buffer. Use avcodec_decode_audio4() instead, which does allow the application to provide a custom get_buffer().

Note:

You might have to align the input buffer avpkt->data and output buffer samples. The alignment requirements depend on the CPU: On some CPUs it isn't necessary at all, on others it won't work at all if not aligned and on others it will work but it will have an impact on performance.

In practice, avpkt->data should have 4 byte alignment at minimum and samples should be 16 byte aligned unless the CPU doesn't need it (AltiVec and SSE do).

Note:

Codecs which have the CODEC_CAP_DELAY capability set have a delay between input and output, these need to be fed with avpkt->data=NULL, avpkt->size=0 at the end to return the remaining frames.

Parameters:

	avctx	the codec context
[out]	samples	the output buffer, sample type in avctx->sample_fmt If the sample format is planar, each channel plane will be the same size, with no padding between channels.
[in,out]	frame_size_ptr	the output buffer size in bytes
[in]	avpkt	The input AVPacket containing the input buffer. You can create such packet with av_init_packet() and by then setting data and size, some decoders might in addition need other fields. All decoders are designed to use the least fields possible though.

Returns:

On error a negative value is returned, otherwise the number of bytes used or zero if no frame data was decompressed (used) from the input AVPacket.

Definition at line 1504 of file utils.c.

int avcodec_decode_audio4	(	AVCodecContext *	avctx,
		AVFrame *	frame,
		int *	got_frame_ptr,
		const AVPacket *	avpkt
	)

Decode the audio frame of size avpkt->size from avpkt->data into frame.

Some decoders may support multiple frames in a single AVPacket. Such decoders would then just decode the first frame. In this case, avcodec_decode_audio4 has to be called again with an AVPacket containing the remaining data in order to decode the second frame, etc... Even if no frames are returned, the packet needs to be fed to the decoder with remaining data until it is completely consumed or an error occurs.

Warning:

The input buffer, avpkt->data must be FF_INPUT_BUFFER_PADDING_SIZE larger than the actual read bytes because some optimized bitstream readers read 32 or 64 bits at once and could read over the end.

Note:

You might have to align the input buffer. The alignment requirements depend on the CPU and the decoder.

Parameters:

	avctx	the codec context
[out]	frame	The AVFrame in which to store decoded audio samples. Decoders request a buffer of a particular size by setting AVFrame.nb_samples prior to calling get_buffer(). The decoder may, however, only utilize part of the buffer by setting AVFrame.nb_samples to a smaller value in the output frame.
[out]	got_frame_ptr	Zero if no frame could be decoded, otherwise it is non-zero.
[in]	avpkt	The input AVPacket containing the input buffer. At least avpkt->data and avpkt->size should be set. Some decoders might also require additional fields to be set.

Returns:

A negative error code is returned if an error occurred during decoding, otherwise the number of bytes consumed from the input AVPacket is returned.

Definition at line 1551 of file utils.c.

Referenced by audio_decode_example(), audio_decode_frame(), avcodec_decode_audio3(), decode_audio(), get_decoded_frame(), main(), try_decode_frame(), and wrap().

int avcodec_decode_subtitle2	(	AVCodecContext *	avctx,
		AVSubtitle *	sub,
		int *	got_sub_ptr,
		AVPacket *	avpkt
	)

Decode a subtitle message.

Return a negative value on error, otherwise return the number of bytes used. If no subtitle could be decompressed, got_sub_ptr is zero. Otherwise, the subtitle is stored in *sub. Note that CODEC_CAP_DR1 is not available for subtitle codecs. This is for simplicity, because the performance difference is expect to be negligible and reusing a get_buffer written for video codecs would probably perform badly due to a potentially very different allocation pattern.

Parameters:

	avctx	the codec context
[out]	sub	The AVSubtitle in which the decoded subtitle will be stored, must be freed with avsubtitle_free if *got_sub_ptr is set.
[in,out]	got_sub_ptr	Zero if no subtitle could be decompressed, otherwise, it is nonzero.
[in]	avpkt	The input AVPacket containing the input buffer.

Definition at line 1598 of file utils.c.

Referenced by subtitle_thread(), transcode_subtitles(), and wrap().

int avcodec_decode_video2	(	AVCodecContext *	avctx,
		AVFrame *	picture,
		int *	got_picture_ptr,
		const AVPacket *	avpkt
	)

Decode the video frame of size avpkt->size from avpkt->data into picture.

Some decoders may support multiple frames in a single AVPacket, such decoders would then just decode the first frame.

Warning:

The input buffer must be FF_INPUT_BUFFER_PADDING_SIZE larger than the actual read bytes because some optimized bitstream readers read 32 or 64 bits at once and could read over the end.

The end of the input buffer buf should be set to 0 to ensure that no overreading happens for damaged MPEG streams.

Note:

You might have to align the input buffer avpkt->data. The alignment requirements depend on the CPU: on some CPUs it isn't necessary at all, on others it won't work at all if not aligned and on others it will work but it will have an impact on performance.

In practice, avpkt->data should have 4 byte alignment at minimum.

Note:

Codecs which have the CODEC_CAP_DELAY capability set have a delay between input and output, these need to be fed with avpkt->data=NULL, avpkt->size=0 at the end to return the remaining frames.

Parameters:

	avctx	the codec context
[out]	picture	The AVFrame in which the decoded video frame will be stored. Use avcodec_alloc_frame to get an AVFrame, the codec will allocate memory for the actual bitmap. with default get/release_buffer(), the decoder frees/reuses the bitmap as it sees fit. with overridden get/release_buffer() (needs CODEC_CAP_DR1) the user decides into what buffer the decoder decodes and the decoder tells the user once it does not need the data anymore, the user app can at this point free/reuse/keep the memory as it sees fit.
[in]	avpkt	The input AVpacket containing the input buffer. You can create such packet with av_init_packet() and by then setting data and size, some decoders might in addition need other fields like flags&AV_PKT_FLAG_KEY. All decoders are designed to use the least fields possible.
[in,out]	got_picture_ptr	Zero if no frame could be decompressed, otherwise, it is nonzero.

Returns:

On error a negative value is returned, otherwise the number of bytes used or zero if no frame could be decompressed.

Definition at line 1439 of file utils.c.

Referenced by decode_video(), ff_load_image(), get_decoded_frame(), get_video_frame(), main(), try_decode_frame(), video_decode_example(), and wrap().

int avcodec_default_get_buffer	(	AVCodecContext *	s,
		AVFrame *	pic
	)

Definition at line 541 of file utils.c.

Referenced by alloc_frame_buffer(), avcodec_decode_audio3(), avcodec_get_context_defaults3(), ff_thread_can_start_frame(), ff_thread_get_buffer(), frame_worker_thread(), and submit_packet().

int avcodec_default_reget_buffer	(	AVCodecContext *	s,
		AVFrame *	pic
	)

Definition at line 589 of file utils.c.

Referenced by avcodec_get_context_defaults3().

void avcodec_default_release_buffer	(	AVCodecContext *	s,
		AVFrame *	pic
	)

Definition at line 553 of file utils.c.

Referenced by avcodec_decode_audio3(), avcodec_get_context_defaults3(), codec_release_buffer(), and free_frame_buffer().

AVCodec* avcodec_find_decoder

(

enum CodecID

id

)

Find a registered decoder with a matching codec ID.

Parameters:

id

CodecID of the requested decoder

Returns:

A decoder if one was found, NULL otherwise.

Definition at line 1723 of file utils.c.

Referenced by add_input_streams(), assert_codec_experimental(), audio_decode_example(), av_find_best_stream(), avcodec_get_name(), avcodec_get_type(), avcodec_string(), avformat_find_stream_info(), choose_decoder(), ff_load_image(), movie_common_init(), open_input_file(), setup_find_stream_info_opts(), stream_component_open(), try_decode_frame(), and video_decode_example().

AVCodec* avcodec_find_decoder_by_name

(

const char *

name

)

Find a registered decoder with the specified name.

Parameters:

name

name of the requested decoder

Returns:

A decoder if one was found, NULL otherwise.

Definition at line 1740 of file utils.c.

Referenced by find_codec_or_die(), stream_component_open(), and v4l2_read_header().

unsigned avcodec_get_edge_width

(

void

)

Return the amount of padding in pixels which the get_buffer callback must provide around the edge of the image for codecs which do not have the CODEC_FLAG_EMU_EDGE flag.

Returns:

Required padding in pixels.

Definition at line 144 of file utils.c.