PR #25375 opened by michaelni URL: https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/25375 Patch URL: https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/25375.patch
The phase mode is the RDFT display with the blue component raised and the red and green components lowered by phase(L) - phase(R), wrapped to (-pi, pi], times the smaller of the red and green components. This shows channels in antiphase, which look the same as channels in phase in the RDFT display. Basically it looks pretty >From 6a28b6e0b175eeb96a25b49d5d3c157799b69901 Mon Sep 17 00:00:00 2001 From: Michael Niedermayer <[email protected]> Date: Thu, 22 Oct 2026 17:53:41 +0200 Subject: [PATCH 1/2] ffplay: show only the DC bin in the bottom row of the RDFT display --- fftools/ffplay.c | 2 -- 1 file changed, 2 deletions(-) diff --git a/fftools/ffplay.c b/fftools/ffplay.c index d17aa1c4224..e7f32136be0 100644 --- a/fftools/ffplay.c +++ b/fftools/ffplay.c @@ -1321,8 +1321,6 @@ static void video_audio_display(VideoState *s) i -= SAMPLE_ARRAY_SIZE; } s->rdft_fn(s->rdft, data[ch], data_in[ch], sizeof(float)); - data[ch][0].im = data[ch][nb_freq].re; - data[ch][nb_freq].re = 0; } /* Least efficient way to do this, we should of course * directly access it but it is more than fast enough. */ -- 2.54.0 >From 522bf7dfb13677ac325ace4b340775e23592234c Mon Sep 17 00:00:00 2001 From: Michael Niedermayer <[email protected]> Date: Thu, 22 Oct 2026 22:27:40 +0200 Subject: [PATCH 2/2] ffplay: add a show mode that colors stereo content by its phase difference The phase mode is the RDFT display with the blue component raised and the red and green components lowered by phase(L) - phase(R), wrapped to (-pi, pi], times the smaller of the red and green components. This shows channels in antiphase, which look the same as channels in phase in the RDFT display. Basically it looks pretty --- doc/ffplay.texi | 3 +++ fftools/ffplay.c | 20 ++++++++++++++++---- 2 files changed, 19 insertions(+), 4 deletions(-) diff --git a/doc/ffplay.texi b/doc/ffplay.texi index 161e369d7f6..2a426f953ec 100644 --- a/doc/ffplay.texi +++ b/doc/ffplay.texi @@ -88,6 +88,9 @@ show video show audio waves @item 2, rdft show audio frequency band using RDFT ((Inverse) Real Discrete Fourier Transform) +@item 3, phase +like rdft, with stereo content whose left channel leads in phase shown in +blue and whose right channel leads shown in yellow @end table Default value is "video", if video is not present or cannot be played diff --git a/fftools/ffplay.c b/fftools/ffplay.c index e7f32136be0..a149ec555c4 100644 --- a/fftools/ffplay.c +++ b/fftools/ffplay.c @@ -278,7 +278,7 @@ typedef struct VideoState { int frame_drops_late; enum ShowMode { - SHOW_MODE_NONE = -1, SHOW_MODE_VIDEO = 0, SHOW_MODE_WAVES, SHOW_MODE_RDFT, SHOW_MODE_NB + SHOW_MODE_NONE = -1, SHOW_MODE_VIDEO = 0, SHOW_MODE_WAVES, SHOW_MODE_RDFT, SHOW_MODE_PHASE, SHOW_MODE_NB } show_mode; int16_t sample_array[SAMPLE_ARRAY_SIZE]; int sample_array_index; @@ -1326,6 +1326,7 @@ static void video_audio_display(VideoState *s) * directly access it but it is more than fast enough. */ if (!SDL_LockTexture(s->vis_texture, &rect, (void **)&pixels, &pitch)) { double w = 1 / sqrt(nb_freq); + int show_phase = s->show_mode == SHOW_MODE_PHASE && nb_display_channels == 2; pitch >>= 2; pixels += pitch * s->height; for (y = 0; y < s->height; y++) { @@ -1334,8 +1335,18 @@ static void video_audio_display(VideoState *s) : a; a = FFMIN(a, 255); b = FFMIN(b, 255); + int blue = (a+b) >> 1; + if (show_phase) { + /* phase(left) - phase(right) in units of pi */ + double phase = atan2(data[0][y].im * data[1][y].re - data[0][y].re * data[1][y].im, + data[0][y].re * data[1][y].re + data[0][y].im * data[1][y].im) / M_PI; + int phase_shift = lrint(phase * FFMIN(a, b)); + a = FFMIN(a - phase_shift / 2, 255); + b = FFMIN(b - phase_shift / 2, 255); + blue = FFMIN(blue + phase_shift, 255); + } pixels -= pitch; - *pixels = (a << 16) + (b << 8) + ((a+b) >> 1); + *pixels = (a << 16) + (b << 8) + blue; } SDL_UnlockTexture(s->vis_texture); } @@ -4356,7 +4367,8 @@ static int opt_show_mode(void *optctx, const char *opt, const char *arg) { show_mode = !strcmp(arg, "video") ? SHOW_MODE_VIDEO : !strcmp(arg, "waves") ? SHOW_MODE_WAVES : - !strcmp(arg, "rdft" ) ? SHOW_MODE_RDFT : SHOW_MODE_NONE; + !strcmp(arg, "rdft" ) ? SHOW_MODE_RDFT : + !strcmp(arg, "phase") ? SHOW_MODE_PHASE : SHOW_MODE_NONE; if (show_mode == SHOW_MODE_NONE) { double num; @@ -4452,7 +4464,7 @@ static const OptionDef options[] = { { "vf", OPT_TYPE_FUNC, OPT_FUNC_ARG | OPT_EXPERT, { .func_arg = opt_add_vfilter }, "set video filters", "filter_graph" }, { "af", OPT_TYPE_STRING, 0, { &afilters }, "set audio filters", "filter_graph" }, { "rdftspeed", OPT_TYPE_INT, OPT_AUDIO | OPT_EXPERT, { &rdftspeed }, "rdft speed", "msecs" }, - { "showmode", OPT_TYPE_FUNC, OPT_FUNC_ARG, { .func_arg = opt_show_mode}, "select show mode (0 = video, 1 = waves, 2 = RDFT)", "mode" }, + { "showmode", OPT_TYPE_FUNC, OPT_FUNC_ARG, { .func_arg = opt_show_mode}, "select show mode (0 = video, 1 = waves, 2 = RDFT, 3 = phase)", "mode" }, { "i", OPT_TYPE_BOOL, 0, { &dummy}, "read specified file", "input_file"}, { "codec", OPT_TYPE_FUNC, OPT_FUNC_ARG, { .func_arg = opt_codec}, "force decoder", "decoder_name" }, { "acodec", OPT_TYPE_STRING, OPT_EXPERT, { &audio_codec_name }, "force audio decoder", "decoder_name" }, -- 2.54.0 _______________________________________________ ffmpeg-devel mailing list -- [email protected] To unsubscribe send an email to [email protected]
