Files | Data Structures | Functions

Rational number calculation. More...


file  rational.h
 Utilties for rational number calculation.

Data Structures

struct  AVRational
 Rational number (pair of numerator and denominator). More...


static AVRational av_make_q (int num, int den)
 Create an AVRational. More...
static int av_cmp_q (AVRational a, AVRational b)
 Compare two rationals. More...
static double av_q2d (AVRational a)
 Convert an AVRational to a double. More...
int av_reduce (int *dst_num, int *dst_den, int64_t num, int64_t den, int64_t max)
 Reduce a fraction. More...
AVRational av_mul_q (AVRational b, AVRational c) av_const
 Multiply two rationals. More...
AVRational av_div_q (AVRational b, AVRational c) av_const
 Divide one rational by another. More...
AVRational av_add_q (AVRational b, AVRational c) av_const
 Add two rationals. More...
AVRational av_sub_q (AVRational b, AVRational c) av_const
 Subtract one rational from another. More...
static av_always_inline AVRational av_inv_q (AVRational q)
 Invert a rational. More...
AVRational av_d2q (double d, int max) av_const
 Convert a double precision floating point number to a rational. More...
int av_nearer_q (AVRational q, AVRational q1, AVRational q2)
 Find which of the two rationals is closer to another rational. More...
int av_find_nearest_q_idx (AVRational q, const AVRational *q_list)
 Find the value in a list of rationals nearest a given reference rational. More...
uint32_t av_q2intfloat (AVRational q)
 Convert an AVRational to a IEEE 32-bit float expressed in fixed-point format. More...

Detailed Description

Rational number calculation.

While rational numbers can be expressed as floating-point numbers, the conversion process is a lossy one, so are floating-point operations. On the other hand, the nature of FFmpeg demands highly accurate calculation of timestamps. This set of rational number utilities serves as a generic interface for manipulating rational numbers as pairs of numerators and denominators.

Many of the functions that operate on AVRational's have the suffix _q, in reference to the mathematical symbol "ℚ" (Q) which denotes the set of all rational numbers.

Function Documentation

static AVRational av_make_q ( int  num,
int  den 
static int av_cmp_q ( AVRational  a,
AVRational  b 
static double av_q2d ( AVRational  a)

Convert an AVRational to a double.

aAVRational to convert
a in floating-point form
See also

Definition at line 104 of file rational.h.

Referenced by audio_thread(), av_dump_format(), av_guess_frame_rate(), av_ts_make_time_string(), avformat_find_stream_info(), avformat_transfer_internal_stream_timing_info(), config_input(), config_output(), config_output_props(), config_props(), configure_video_device(), decode_frame(), decode_syncpoint(), DEFINE_BLEND8(), defined_frame_rate(), do_blend(), do_video_out(), do_video_stats(), draw_text(), dump_mastering_display_metadata(), dump_stream_format(), dv_write_pack(), estimate_timings(), fbdev_read_header(), fbdev_read_packet(), ff_decklink_set_format(), ff_determine_signal_peak(), ff_inlink_evaluate_timeline_at_frame(), ff_inlink_process_commands(), ff_mpv_encode_init(), ff_mpv_encode_picture(), ff_rfps_add_frame(), ff_rfps_calculate(), film_write_header(), filter_frame(), flv_write_header(), gdigrab_read_header(), gdigrab_read_packet(), geq_filter_frame(), get_best_frame(), get_fps(), get_video_frame(), init(), init_muxer(), init_output_stream_encode(), init_stream(), init_video(), main(), match_framerate(), mkv_write_trailer(), mkv_write_video_color(), mov_write_trak_tag(), mpegvideo_parse(), output_single_frame(), pkt_dump_internal(), process_input_packet(), put_videoinfoheader2(), read_header(), read_seek(), read_thread(), request_frame(), seg_write_packet(), segment_end(), select_frame(), set_side_data(), stream_has_enough_packets(), svc_encode_init(), thp_read_header(), v4l2_read_header(), vaapi_encode_h265_init_picture_params(), vaapi_encode_mpeg2_init_sequence_params(), video_thread(), write_manifest(), and writer_print_time().

int av_reduce ( int dst_num,
int dst_den,
int64_t  num,
int64_t  den,
int64_t  max 

Reduce a fraction.

This is useful for framerate calculations.

[out]dst_numDestination numerator
[out]dst_denDestination denominator
[in]numSource numerator
[in]denSource denominator
[in]maxMaximum allowed values for dst_num & dst_den
1 if the operation is exact, 0 otherwise

Definition at line 35 of file rational.c.

Referenced by apng_write_header(), asf_read_header(), av1_metadata_update_sequence_header(), av_add_q(), av_d2q(), av_guess_sample_aspect_ratio(), av_mul_q(), av_parse_ratio(), avcodec_string(), avformat_find_stream_info(), avformat_transfer_internal_stream_timing_info(), avi_write_header(), avpriv_set_pts_info(), compute_dar(), config_input(), config_output(), cudascale_filter_frame(), decode_frame(), decode_sequence_header_adv(), dnxhd_decode_header(), dump_stream_format(), dxa_read_header(), export_stream_params(), ff_audio_resample_init(), ff_canopus_parse_info_tag(), ff_compute_frame_duration(), ff_mpv_encode_init(), ff_rfps_calculate(), ff_rm_read_mdpr_codecdata(), filter_frame(), flush_packet(), get_aspect_ratio(), h264_metadata_update_sps(), h264_slice_header_init(), h265_metadata_update_sps(), h265_metadata_update_vps(), hevc_parse_slice_header(), init_output_stream_encode(), jp2_find_codestream(), jpeg_put_comments(), libx265_encode_init(), matroska_parse_tracks(), mkv_write_track(), mov_read_header(), mov_read_pasp(), mov_read_trak(), mov_write_pasp_tag(), mpeg2_metadata_update_fragment(), mpeg4_encode_vol_header(), mpeg_decode_postinit(), mxf_parse_dnxhd_frame(), mxf_parse_h264_frame(), mxf_parse_mpeg2_frame(), nppscale_filter_frame(), parse_video_var(), pcx_encode_frame(), put_videoinfoheader2(), qsvscale_filter_frame(), read_fps(), read_huffman_tree(), rebuild_filter_bank_with_compensation(), resample_init(), set_sar(), show_stream(), skeleton_header(), smacker_read_header(), svc_encode_init(), tmv_read_header(), vaapi_encode_h264_init_sequence_params(), vaapi_encode_h265_init_sequence_params(), vaapi_encode_init_rate_control(), vaapi_encode_mjpeg_init_picture_params(), vmd_read_header(), vtenc_create_encoder(), X264_init(), xvid_encode_frame(), yuv4_generate_header(), and yuv4_read_header().

AVRational av_mul_q ( AVRational  b,
AVRational  c 
) const
AVRational av_div_q ( AVRational  b,
AVRational  c 
) const
AVRational av_add_q ( AVRational  b,
AVRational  c 
) const

Add two rationals.

bFirst rational
cSecond rational

Definition at line 93 of file rational.c.

Referenced by av_sub_q(), init_output_stream(), init_output_stream_streamcopy(), and main().

AVRational av_sub_q ( AVRational  b,
AVRational  c 
) const

Subtract one rational from another.

bFirst rational
cSecond rational

Definition at line 101 of file rational.c.

Referenced by ff_mxf_get_content_package_rate(), ff_mxf_get_samples_per_frame(), and main().

static av_always_inline AVRational av_inv_q ( AVRational  q)

Invert a rational.

1 / q
transcoding.c, and vaapi_transcode.c.

Definition at line 159 of file rational.h.

Referenced by activate(), avcodec_open2(), avformat_find_stream_info(), avformat_transfer_internal_stream_timing_info(), avi_read_header(), build_frame_code(), check_size(), config_input(), config_output(), config_props(), config_video(), configure_input_video_filter(), dec_enc(), decode_simple_internal(), decode_vol_header(), decode_vop_header(), dshow_add_device(), dv_extract_video_info(), dvvideo_decode_frame(), ff_compute_frame_duration(), ff_guess_coded_bitrate(), ff_rfps_calculate(), film_write_header(), find_fps(), find_frame_rate_index(), gdigrab_read_header(), h264_parse(), init(), init_output_stream_encode(), init_src(), init_video_stream(), mkv_write_track(), mov_create_timecode_track(), mov_parse_stsd_data(), mpegvideo_extract_headers(), mv_read_header(), mxf_compute_sample_count(), mxf_handle_missing_index_segment(), mxf_parse_structural_metadata(), mxf_read_seek(), mxf_set_audio_pts(), mxf_set_current_edit_unit(), mxf_write_header(), open_output_file(), process_input_packet(), process_work_frame(), program_opencl_config_output(), r3d_read_rdvo(), r3d_seek(), read_header(), rm_write_header(), seek_to_start(), smush_read_header(), source_config_props(), txd_read_header(), vaapi_encode_mpeg2_init_sequence_params(), vc1_extract_header(), decklink_input_callback::VideoInputFrameArrived(), viv_read_seek(), vivo_read_header(), write_packet(), and yuv4_read_header().

AVRational av_d2q ( double  d,
int  max 
) const

Convert a double precision floating point number to a rational.

In case of infinity, the returned value is expressed as {1, 0} or {-1, 0} depending on the sign.

ddouble to convert
maxMaximum allowed numerator and denominator
d in AVRational form
See also

Definition at line 106 of file rational.c.

Referenced by amf_parse_object(), av_inv_q(), av_opt_get_q(), av_opt_get_video_rate(), av_opt_is_set_to_default(), av_opt_set_defaults2(), av_parse_ratio(), config_output_props(), davs2_dump_frames(), decode_frame(), decode_header(), ff_update_hdr_metadata(), fourxm_read_header(), get_aspect_ratio(), microdvd_read_header(), mov_read_tkhd(), mov_read_trak(), mpeg_decode_postinit(), nuv_header(), opt_list(), read_header(), thp_read_header(), var_read_float(), and write_number().

int av_nearer_q ( AVRational  q,
AVRational  q1,
AVRational  q2 

Find which of the two rationals is closer to another rational.

qRational to be compared against
q1,q2Rationals to be tested
One of the following values:
  • 1 if q1 is nearer to q than q2
  • -1 if q2 is nearer to q than q1
  • 0 if they have the same distance

Definition at line 127 of file rational.c.

Referenced by av_find_nearest_q_idx(), av_inv_q(), and find_frame_rate_index().

int av_find_nearest_q_idx ( AVRational  q,
const AVRational q_list 

Find the value in a list of rationals nearest a given reference rational.

qReference rational
q_listArray of rationals terminated by {0, 0}
Index of the nearest value found in the array

Definition at line 142 of file rational.c.

Referenced by av_inv_q(), ff_mxf_get_content_package_rate(), ff_mxf_get_samples_per_frame(), and init_output_stream_encode().

uint32_t av_q2intfloat ( AVRational  q)

Convert an AVRational to a IEEE 32-bit float expressed in fixed-point format.

qRational to be converted
Equivalent floating-point value, expressed as an unsigned 32-bit integer.
The returned value is platform-indepedant.

Definition at line 152 of file rational.c.

Referenced by av_inv_q(), ircam_write_header(), and main().