better json support

[ralyodio]

Can we get a way to output json to STDOUT?

[KitaitiMakoto]

Whisper.cpp provides API for logging: whisper_log_set
Using it, you may customize logging format.

[KitaitiMakoto]

Also, you may set callback called on new segment: new_segment_callback

require "whisper"
require "json"

# Set log callback to convert log to JSON format
Whisper.log_set ->(level, text, _) {
  puts ({
    level: level,
    text:  text
  }).to_json
}, nil

whisper = Whisper::Context.new("../../models/ggml-base.bin")
params = Whisper::Params.new

# Helper function
def format_time(time_ms)
  sec, decimal_part = time_ms.divmod(1000)
  min, sec = sec.divmod(60)
  hour, min = min.divmod(60)
  "%02d:%02d:%02d.%03d" % [hour, min, sec, decimal_part]
end

# Set new segment callback to convert transcription result to JSON format
params.on_new_segment do |segment|
  puts ({
    start_time: format_time(segment.start_time),
    end_time:   format_time(segment.end_time),
    text:       segment.text
  }).to_json
end

whisper.transcribe("../../samples/jfk.wav", params)

{"level":2,"text":"whisper_init_from_file_with_params_no_state: loading model from '../../models/ggml-base.bin'\n"}
{"level":2,"text":"whisper_init_with_params_no_state: use gpu    = 1\n"}
{"level":2,"text":"whisper_init_with_params_no_state: flash attn = 0\n"}
  :
  :
(snip)
  :
  :
{"level":2,"text":"whisper_init_state: compute buffer (cross)  =    4.65 MB\n"}
{"level":2,"text":"whisper_init_state: compute buffer (decode) =   97.27 MB\n"}
{"start_time":"00:00:00.000","end_time":"00:00:07.600","text":" And so my fellow Americans, ask not what your country can do for you,"}
{"start_time":"00:00:07.600","end_time":"00:00:10.600","text":" ask what you can do for your country."}

I used Ruby because I'm not familiar with C/C++, though essentially we should be able to do the same thing in C/C++.