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|
let () = Printexc.record_backtrace true
let () =
if Array.length Sys.argv < 4 then (
Printf.eprintf
" usage: %s <input file> <output file> <output codec>\n\
\ API example program to show how to read audio frames from an \
input file using the streaming API.\n\
\ This program parse data to packets from a file, decodes them, and \
writes decoded\n\
\ audio frames to a audio file named <output file>.\n"
Sys.argv.(0);
exit 1);
Avutil.Log.set_callback (fun _ -> ());
let in_fd = Unix.openfile Sys.argv.(1) [Unix.O_RDONLY] 0 in
let out_file = Av.open_output Sys.argv.(2) in
let codec = Avcodec.Audio.find_encoder_by_name Sys.argv.(3) in
let channel_layout =
Avcodec.Audio.find_best_channel_layout codec Avutil.Channel_layout.stereo
in
let sample_format = Avcodec.Audio.find_best_sample_format codec `Dbl in
let sample_rate = Avcodec.Audio.find_best_sample_rate codec 44100 in
let time_base = { Avutil.num = 1; den = sample_rate } in
let out_stream =
Av.new_audio_stream ~channel_layout ~sample_format ~sample_rate ~time_base
~codec out_file
in
let filter = ref None in
let get_filter frame =
match !filter with
| Some f -> f
| None ->
let in_params =
{
Avfilter.Utils.sample_rate =
Avutil.Audio.frame_get_sample_rate frame;
channel_layout = Avutil.Audio.frame_get_channel_layout frame;
sample_format = Avutil.Audio.frame_get_sample_format frame;
}
in
let in_time_base = { Avutil.num = 1; den = sample_rate } in
let out_frame_size =
if List.mem `Variable_frame_size (Avcodec.capabilities codec) then
512
else Av.get_frame_size out_stream
in
let out_params =
{ Avfilter.Utils.sample_rate; sample_format; channel_layout }
in
let f =
Avfilter.Utils.init_audio_converter ~in_params ~in_time_base
~out_params ~out_frame_size ()
in
filter := Some f;
f
in
let pts = ref 0L in
let on_frame frame =
Avutil.Frame.set_pts frame (Some !pts);
pts := Int64.add !pts (Int64.of_int (Avutil.Audio.frame_nb_samples frame));
Av.write_frame out_stream frame
in
let write_frame frame =
let filter = get_filter frame in
Avfilter.Utils.convert_audio filter on_frame (`Frame frame)
in
let read = Unix.read in_fd in
let seek = Unix.lseek in_fd in
let container = Av.open_input_stream ~seek read in
let idx, stream, params = Av.find_best_audio_stream container in
let codec_id = Avcodec.Audio.get_params_id params in
let sample_format =
match Avcodec.Audio.get_sample_format params with
| `Dbl -> "dbl"
| `Dblp -> "dblp"
| `Flt -> "flt"
| `Fltp -> "fltp"
| `None -> "none"
| `S16 -> "s16"
| `S16p -> "s16p"
| `S32 -> "s32"
| `S32p -> "s32p"
| `S64 -> "s64"
| `S64p -> "s64p"
| `U8 -> "u8"
| `U8p -> "u8p"
in
Printf.printf "Detected format: %s, %dHz, %d channels, %s\n%!"
(Avcodec.Audio.string_of_id codec_id)
(Avcodec.Audio.get_sample_rate params)
(Avcodec.Audio.get_nb_channels params)
sample_format;
let rec f () =
try
(match Av.read_input container ~audio_frame:[stream] with
| `Audio_frame (i, frame) when i = idx -> write_frame frame
| _ -> assert false);
f ()
with
| Avutil.Error `Eof ->
Avfilter.Utils.convert_audio (Option.get !filter) on_frame `Flush
| Avutil.Error `Invalid_data -> f ()
in
f ();
Unix.close in_fd;
Av.close container;
Av.close out_file;
Gc.full_major ();
Gc.full_major ()
|
