Rational number calculation. More...

Files
file	rational.h
	Utilties for rational number calculation.

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

Functions
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

◆ av_make_q()

static AVRational av_make_q	(	int	num,
		int	den
	)

inlinestatic

Create an AVRational.

Useful for compilers that do not support compound literals.

Note: The return value is not reduced.

See also: av_reduce()

Definition at line 71 of file rational.h.

Referenced by alloc_out_frame(), avf_read_packet(), config_out_props(), config_output(), config_props(), convert_sub_to_old_ass_form(), decode_frame_common(), encode_frame(), ff_decklink_read_header(), ff_decklink_set_format(), ff_framequeue_skip_samples(), ff_mediacodec_dec_send(), filter_frame(), init_output_stream_encode(), mediacodec_wrap_hw_buffer(), mediacodec_wrap_sw_buffer(), mkv_parse_video_color(), mov_metadata_hmmt(), mov_read_mdcv(), mov_read_sidx(), mov_read_smdm(), ndi_create_video_stream(), parse_manifest_representation(), plot_cqt(), push_frame(), and request_frame().

◆ av_cmp_q()

static int av_cmp_q	(	AVRational	a,
		AVRational	b
	)

inlinestatic

Compare two rationals.

Parameters

a	First rational
b	Second rational

Returns

One of the following values:

0 if a == b
1 if a > b
-1 if a < b
INT_MIN if one of the values is of the form 0 / 0

Definition at line 89 of file rational.h.

Referenced by av_nearer_q(), av_opt_is_set_to_default(), compute_display_area(), compute_texture_rect(), config_input(), config_out_props(), config_output(), dash_init(), dump_stream_format(), ff_decklink_set_format(), ff_h263_aspect_to_info(), ff_mpeg12_find_best_frame_rate(), ff_mxf_get_samples_per_frame(), filter_frame(), find_frame_rate_index(), h264_init_ps(), init_muxer(), main(), mkv_write_track(), mpeg_decode_postinit(), opengl_compute_display_area(), update_pts(), vaapi_encode_mpeg2_init_sequence_params(), and write_adaptation_set().

◆ av_q2d()

static double av_q2d ( AVRational a )

inlinestatic

Convert an AVRational to a double.

Parameters

a	AVRational to convert

Returns: a in floating-point form

See also: av_d2q()

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(), calculate_display_rect(), config_input(), config_output(), config_output_props(), config_props(), configure_video_device(), decode_frame(), decode_syncpoint(), DEFINE_BLEND8(), defined_frame_rate(), determine_signal_peak(), 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_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(), mxf_compute_sample_count(), ndi_setup_video(), output_single_frame(), pkt_dump_internal(), process_input_packet(), push_frame(), 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_mpeg2_init_sequence_params(), video_thread(), write_manifest(), and writer_print_time().

◆ av_reduce()

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.

Parameters

[out]	dst_num	Destination numerator
[out]	dst_den	Destination denominator
[in]	num	Source numerator
[in]	den	Source denominator
[in]	max	Maximum allowed values for `dst_num` & `dst_den`

Returns: 1 if the operation is exact, 0 otherwise

Definition at line 35 of file rational.c.

Referenced by apng_write_header(), asf_read_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_mpeg2_frame(), ndi_create_video_stream(), ndi_setup_video(), nppscale_filter_frame(), nvenc_setup_encoder(), 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(), tmv_read_header(), vaapi_encode_init_rate_control(), vmd_read_header(), vtenc_create_encoder(), X264_init(), xvid_encode_frame(), yuv4_generate_header(), and yuv4_read_header().

◆ av_mul_q()

AVRational av_mul_q	(	AVRational	b,
		AVRational	c
	)		const

Multiply two rationals.

Parameters

b	First rational
c	Second rational

Returns: b*c

Definition at line 80 of file rational.c.

Referenced by av_add_stable(), av_div_q(), avcodec_open2(), avformat_find_stream_info(), avi_write_header(), compute_display_area(), compute_pkt_fields(), compute_texture_rect(), config_input(), config_out_props(), config_output(), config_props(), cudascale_config_props(), decode_simple_internal(), decode_vol_header(), decode_vop_header(), deint_vaapi_config_output(), encode_frame(), ff_compute_frame_duration(), ff_mpeg12_find_best_frame_rate(), filter_frame(), find_frame_rate_index(), h264_parse(), init_output_stream_encode(), init_output_stream_streamcopy(), mpeg_decode_postinit(), mpegvideo_extract_headers(), mxf_compute_sample_count(), ndi_create_video_stream(), nppscale_config_props(), opengl_compute_display_area(), put_videoinfoheader2(), qsvdeint_config_props(), qsvscale_config_props(), rv20_decode_picture_header(), scale_vaapi_config_output(), update_sar(), and vc1_extract_header().

◆ av_div_q()

AVRational av_div_q	(	AVRational	b,
		AVRational	c
	)		const

Divide one rational by another.

Parameters

b	First rational
c	Second rational

Returns: b/c

Definition at line 88 of file rational.c.

Referenced by av_dv_codec_profile2(), av_guess_frame_rate(), avi_read_header(), build_frame_code(), config_input(), config_output(), config_output_props(), config_props(), config_props_output(), ff_mpeg12_find_best_frame_rate(), mediacodec_dec_parse_format(), mpeg_decode_postinit(), and vaapi_encode_mpeg2_init_sequence_params().

◆ av_add_q()

AVRational av_add_q	(	AVRational	b,
		AVRational	c
	)		const

Add two rationals.

Parameters

b	First rational
c	Second rational

Returns: b+c

Definition at line 93 of file rational.c.

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

◆ av_sub_q()

AVRational av_sub_q	(	AVRational	b,
		AVRational	c
	)		const

Subtract one rational from another.

Parameters

b	First rational
c	Second rational

Returns: b-c

Definition at line 101 of file rational.c.

Referenced by ff_mxf_get_samples_per_frame(), and main().

◆ av_inv_q()

static av_always_inline AVRational av_inv_q ( AVRational q )

static

Invert a rational.

Parameters

q value

Returns: 1 / q

Examples:: transcoding.c, and vaapi_transcode.c.

Definition at line 159 of file rational.h.

Referenced by avcodec_open2(), avformat_find_stream_info(), avformat_transfer_internal_stream_timing_info(), avi_read_header(), build_frame_code(), config_output(), config_props(), 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_parse_structural_metadata(), mxf_read_seek(), 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(), vivo_read_header(), write_packet(), and yuv4_read_header().

◆ av_d2q()

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.

Parameters

d	`double` to convert
max	Maximum allowed numerator and denominator

Returns: d in AVRational form

See also: av_q2d()

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(), decode_frame(), decode_header(), fourxm_read_header(), get_aspect_ratio(), microdvd_read_header(), mov_read_tkhd(), mov_read_trak(), mpeg_decode_postinit(), ndi_create_video_stream(), nuv_header(), opt_list(), read_header(), thp_read_header(), var_read_float(), and write_number().

◆ av_nearer_q()

int av_nearer_q	(	AVRational	q,
		AVRational	q1,
		AVRational	q2
	)

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

Parameters

q	Rational to be compared against
q1,q2	Rationals to be tested

Returns

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().

◆ av_find_nearest_q_idx()

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.

Parameters

q	Reference rational
q_list	Array of rationals terminated by `{0, 0}`

Returns: 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_samples_per_frame(), and init_output_stream_encode().

◆ av_q2intfloat()

uint32_t av_q2intfloat ( AVRational q )

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

Parameters

q	Rational to be converted

Returns: Equivalent floating-point value, expressed as an unsigned 32-bit integer.

Note: The returned value is platform-indepedant.

Definition at line 152 of file rational.c.

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

Files

Data Structures

Functions

Detailed Description

Function Documentation

◆ av_make_q()

◆ av_cmp_q()

◆ av_q2d()

◆ av_reduce()

◆ av_mul_q()

◆ av_div_q()

◆ av_add_q()

◆ av_sub_q()

◆ av_inv_q()

◆ av_d2q()

◆ av_nearer_q()

◆ av_find_nearest_q_idx()

◆ av_q2intfloat()