FFmpeg
 All Data Structures Namespaces Files Functions Variables Typedefs Enumerations Enumerator Macros Groups Pages
Files | Data Structures | Functions
AVRational

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

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

Convert an AVRational to a double.

Parameters
aAVRational 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(), 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(), 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(), read_header(), read_seek(), read_thread(), request_frame(), seg_write_packet(), segment_end(), select_frame(), set_side_data(), set_work_frame_pts(), stream_has_enough_packets(), svc_encode_init(), thp_read_header(), update(), v4l2_read_header(), 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.

Parameters
[out]dst_numDestination numerator
[out]dst_denDestination denominator
[in]numSource numerator
[in]denSource denominator
[in]maxMaximum 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_mpv_encode_init(), ff_rfps_calculate(), ff_rm_read_mdpr_codecdata(), filter_frame(), flush_packet(), 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(), mov_read_header(), mov_read_pasp(), mov_read_trak(), mov_write_pasp_tag(), mpeg2_metadata_update_fragment(), mpeg4_encode_vol_header(), mxf_parse_mpeg2_frame(), ndi_setup_video(), nppscale_filter_frame(), nvenc_setup_encoder(), parse_video_var(), pcx_encode_frame(), qsvscale_filter_frame(), read_fps(), 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().

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.

Parameters
bFirst rational
cSecond 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().

AVRational av_sub_q ( AVRational  b,
AVRational  c 
) const

Subtract one rational from another.

Parameters
bFirst rational
cSecond rational
Returns
b-c

Definition at line 101 of file rational.c.

Referenced by ff_mxf_get_samples_per_frame(), and main().

static av_always_inline AVRational av_inv_q ( AVRational  q)
static
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
ddouble to convert
maxMaximum 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_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().

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

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

Parameters
qRational to be compared against
q1,q2Rationals 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(), 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.

Parameters
qReference rational
q_listArray 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 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.

Parameters
qRational 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 ircam_write_header(), and main().