vad : revisit timestamp alignment/mapping

[danbev]

This commit improving the timestamp alignment by introducing a mapping table, adding intermediate reference points for longer segments, and binary search for lookups.

The motivation for this changes is to address issues with the currently solution where zero-length segments are possible, and also to improve the precision of the VAD timestamps.

Refs: #3162

---

Notes regarding the changes can be found here.

[ggerganov]

This change seems to not be compatible with the -p parameter. For example:

./bin/whisper-cli -m ../models/ggml-large-v3-turbo.bin -f ../samples/gb0.wav --vad --vad-model ../models/silero-v5.1.2-ggml.bin -fa -p 2

The second half of the transcription has the same repeating timestamp for all segments.

[00:00:00.000 --> 00:00:03.250]   - Good morning, this Tuesday is election day.
[00:00:03.250 --> 00:00:05.950]   After months of spirited debate and vigorous campaigning,
[00:00:05.950 --> 00:00:08.570]   the time has come for Americans to make important decisions
[00:00:08.570 --> 00:00:10.150]   about our nation's future.
[00:00:10.150 --> 00:00:13.750]   I encourage all Americans to go to the polls and vote.
[00:00:13.750 --> 00:00:16.100]   Election season brings out the spirit of competition
[00:00:16.100 --> 00:00:18.020]   between our political parties.
[00:00:18.020 --> 00:00:20.210]   And that competition is an essential part
[00:00:20.210 --> 00:00:21.760]   of a healthy democracy.
[00:00:21.760 --> 00:00:23.520]   But as the campaigns come to a close,
[00:00:23.520 --> 00:00:25.920]   Republicans, Democrats, and Independents
[00:00:25.920 --> 00:00:29.120]   can find common ground on at least one point.
[00:00:29.120 --> 00:00:31.510]   Our system of representative democracy
[00:00:31.510 --> 00:00:34.440]   is one of America's greatest strengths.
[00:00:34.440 --> 00:00:36.220]   The United States was founded on the belief
[00:00:36.220 --> 00:00:38.280]   that all men are created equal.
[00:00:38.280 --> 00:00:41.440]   Every election day, millions of Americans of all races,
[00:00:41.440 --> 00:00:43.810]   religions, and backgrounds step into voting booths
[00:00:43.810 --> 00:00:45.300]   throughout the nation.
[00:00:45.300 --> 00:00:47.730]   Whether they are rich or poor, old or young,
[00:00:47.730 --> 00:00:50.640]   each of them has an equal share in choosing the path
[00:00:50.640 --> 00:00:52.450]   that our country will take.
[00:00:52.450 --> 00:00:54.870]   And every ballot they cast is a reminder
[00:00:54.870 --> 00:00:58.290]   that our founding principles are alive and well.
[00:00:58.290 --> 00:00:59.720]   Voting is one of the great privileges
[00:00:59.720 --> 00:01:01.780]   of American citizenship.
[00:01:01.780 --> 00:01:03.680]   and it has always required brave defenders.
[00:01:03.680 --> 00:01:03.780]   As you head to the polls next week, remember the sacrifices that have been made by generations of Americans in uniform to preserve our way of life.
[00:01:03.680 --> 00:01:03.780]   From Bunker Hill to Baghdad, the men and women of American armed forces have been devoted guardians of our democracy.
[00:01:03.680 --> 00:01:03.780]   All of us owe them and their families a special debt of gratitude on Election Day.
[00:01:03.680 --> 00:01:03.780]   Americans should also remember the important example that our elections set throughout the world.
[00:01:03.680 --> 00:01:03.780]   Young democracies from Georgia and Ukraine to Afghanistan and Iraq can look to the United States for proof that self-government can endure.
[00:01:03.680 --> 00:01:03.780]   And nations that still live under tyranny and oppression can find hope and inspiration in our commitment to liberty.
[00:01:03.680 --> 00:01:03.780]   For more than two centuries, Americans have demonstrated the ability of free people to choose their own leaders.
[00:01:03.680 --> 00:01:03.780]   Our nation has flourished because of its commitment to trusting the wisdom of our citizenry.
[00:01:03.680 --> 00:01:03.780]   In this year's election, we will see this tradition continue.
[00:01:03.680 --> 00:01:03.780]   And we will be reminded once again that we are blessed to live in a free nation guided by the will of the people.
[00:01:03.680 --> 00:01:03.780]   Thank you for listening.
ggml_metal_free: deallocating
whisper_full_parallel: the audio has been split into 2 chunks at the following times:
whisper_full_parallel: split 1 - 00:01:03.670
whisper_full_parallel: the transcription quality may be degraded near these boundaries

[danbev]

@ggerganov I had not tried this with -p/--processors and did not notice this. Thanks, I'll look into it.