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.

Examples:

doc/examples/decoding_encoding.c.

Definition at line 580 of file avcodec.h.

Referenced by a64multi_init_encoder(), aac_adtstoasc_filter(), aac_decode_frame(), aac_encode_init(), aacPlus_encode_init(), add_av_stream1(), adpcm_encode_init(), alac_encode_init(), alloc_and_copy(), alloc_buffers(), asf_parse_packet(), asf_read_stream_properties(), atrac3_decode_init(), audio_decode_example(), av_fast_padded_malloc(), av_fast_padded_mallocz(), av_grow_packet(), av_packet_from_data(), 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_decode_subtitle2(), avcodec_encode_audio2(), avcodec_encode_video2(), avi_read_header(), avio_close_dyn_buf(), avui_encode_init(), cdxl_decode_frame(), codec_reinit(), cook_decode_init(), dca_parse_params(), decode_frame(), decode_i_frame(), decode_init(), decode_p_frame(), decode_plane(), dshow_add_device(), dump_extradata(), dv_decode_video_segment(), encode_init(), extract_header(), extract_mpeg4_header(), Faac_encode_init(), ff_alloc_extradata(), ff_alloc_packet2(), ff_combine_frame(), ff_h263_decode_frame(), ff_h264_decode_nal(), ff_hevc_extract_rbsp(), ff_id3v2_parse_apic(), ff_mjpeg_find_marker(), ff_mpeg_update_thread_context(), fixup_vorbis_headers(), flac_read_header(), flic_decode_frame_8BPP(), flv_queue_extradata(), g2m_init_buffers(), h264_extradata_to_annexb(), h264_mp4toannexb_filter(), h264_new_context(), handle_packets(), iff_read_header(), imx_dump_header(), jacosub_read_header(), jpg_decode_data(), latm_decode_audio_specific_config(), libopus_encode_init(), mjpega_dump_header(), mov2textsub(), mov_read_extradata(), mov_read_stsz(), mov_write_dvc1_structs(), mp3_header_compress(), mp3_header_decompress(), mp_decode_frame(), mpc8_parse_seektable(), mpegts_push_data(), mss2_decode_frame(), mxg_update_cache(), new_pes_packet(), noise(), ogg_new_buf(), ogg_new_stream(), ogg_read_page(), ogg_save(), oggvorbis_encode_init(), ogm_header(), packet_alloc(), parse_fmtp_config(), parse_packed_headers(), pcx_decode_frame(), qt_rtp_parse_packet(), rdt_parse_b64buf(), read_apic(), read_header(), read_kuki_chunk(), recode_subtitle(), redspark_read_header(), rm_read_audio_stream_info(), sdp_parse_fmtp_config_h264(), shorten_decode_frame(), spdif_write_packet(), Stagefright_init(), submit_packet(), svq3_decode_frame(), tak_read_header(), text2movsub(), theora_header(), tiff_unpack_fax(), transcode_init(), utvideo_encode_frame(), utvideo_encode_init(), vc1_decode_frame(), vc1_decode_init(), vc1_extract_headers(), vfw_read_header(), video_decode_example(), wma_decode_superframe(), write_frame(), wv_get_value_float(), and xwma_read_header().

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 610 of file avcodec.h.

Find a registered decoder with a matching codec ID.

Parameters

id AVCodecID of the requested decoder

Returns

A decoder if one was found, NULL otherwise.

Examples:

doc/examples/decoding_encoding.c, and doc/examples/demuxing.c.

Definition at line 2620 of file utils.c.

Referenced by add_input_streams(), audio_decode_example(), avcodec_get_name(), avcodec_get_type(), avcodec_open2(), avcodec_string(), choose_decoder(), dshow_cycle_formats(), ff_load_image(), filter_codec_opts(), find_codec_or_die(), find_decoder(), list_formats(), open_codec_context(), open_input_file(), open_stream(), show_codecs(), smvjpeg_decode_init(), stream_component_open(), and video_decode_example().

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 2625 of file utils.c.

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

The default callback for AVCodecContext.get_buffer2().

It is made public so it can be called by custom get_buffer2() implementations for decoders without CODEC_CAP_DR1 set.

Definition at line 694 of file utils.c.

Referenced by alloc_frame_buffer(), avcodec_get_context_defaults3(), ff_thread_release_buffer(), submit_packet(), and thread_get_buffer_internal().

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 229 of file utils.c.

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 394 of file utils.c.

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 248 of file utils.c.

Referenced by avcodec_align_dimensions(), and update_frame_pool().

Converts AVChromaLocation to swscale x/y chroma position.

The positions represent the chroma (0,0) position in a coordinates system with luma (0,0) representing the origin and luma(1,1) representing 256,256

Parameters

xpos horizontal chroma sample position

ypos vertical chroma sample position

Definition at line 409 of file utils.c.

Referenced by avcodec_chroma_pos_to_enum().

Converts swscale x/y chroma position to AVChromaLocation.

The positions represent the chroma (0,0) position in a coordinates system with luma (0,0) representing the origin and luma(1,1) representing 256,256

Parameters

xpos horizontal chroma sample position

ypos vertical chroma sample position

Definition at line 421 of file utils.c.

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 and the return value would be less than the packet size. 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.

Some decoders (those marked with CODEC_CAP_DELAY) have a delay between input and output. This means that for some packets they will not immediately produce decoded output and need to be flushed at the end of decoding to get all the decoded data. Flushing is done by calling this function with packets with avpkt->data set to NULL and avpkt->size set to 0 until it stops returning samples. It is safe to flush even those decoders that are not marked with CODEC_CAP_DELAY, then no samples will be returned.

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.

Parameters

avctx the codec context

[out] frame The AVFrame in which to store decoded audio samples. The decoder will allocate a buffer for the decoded frame by calling the AVCodecContext.get_buffer2() callback. When AVCodecContext.refcounted_frames is set to 1, the frame is reference counted and the returned reference belongs to the caller. The caller must release the frame using av_frame_unref() when the frame is no longer needed. The caller may safely write to the frame if av_frame_is_writable() returns 1. When AVCodecContext.refcounted_frames is set to 0, the returned reference belongs to the decoder and is valid only until the next call to this function or until closing or flushing the decoder. The caller may not write to it.

[out] got_frame_ptr Zero if no frame could be decoded, otherwise it is non-zero. Note that this field being set to zero does not mean that an error has occurred. For decoders with CODEC_CAP_DELAY set, no given decode call is guaranteed to produce a frame.

[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.

Examples:

doc/examples/decoding_encoding.c, doc/examples/demuxing.c, and doc/examples/filtering_audio.c.

Definition at line 2167 of file utils.c.

Referenced by audio_decode_example(), audio_decode_frame(), decode_audio(), decode_packet(), main(), movie_push_frame(), process_frame(), try_decode_frame(), and wrap().

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

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 av_frame_alloc() to get an AVFrame. The codec will allocate memory for the actual bitmap by calling the AVCodecContext.get_buffer2() callback. When AVCodecContext.refcounted_frames is set to 1, the frame is reference counted and the returned reference belongs to the caller. The caller must release the frame using av_frame_unref() when the frame is no longer needed. The caller may safely write to the frame if av_frame_is_writable() returns 1. When AVCodecContext.refcounted_frames is set to 0, the returned reference belongs to the decoder and is valid only until the next call to this function or until closing or flushing the decoder. The caller may not write to it.

[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.

Examples:

doc/examples/decoding_encoding.c, doc/examples/demuxing.c, and doc/examples/filtering_video.c.

Definition at line 2028 of file utils.c.

Referenced by decode_packet(), decode_video(), decode_write_frame(), ff_load_image(), get_video_frame(), main(), movie_push_frame(), process_frame(), smvjpeg_decode_frame(), try_decode_frame(), and wrap().

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.

Some decoders (those marked with CODEC_CAP_DELAY) have a delay between input and output. This means that for some packets they will not immediately produce decoded output and need to be flushed at the end of decoding to get all the decoded data. Flushing is done by calling this function with packets with avpkt->data set to NULL and avpkt->size set to 0 until it stops returning subtitles. It is safe to flush even those decoders that are not marked with CODEC_CAP_DELAY, then no subtitles will be returned.

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 2393 of file utils.c.

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