module Lame: sig
.. end
Bindings to the lame library to encode mp3 files.
Author(s): Samuel Mimram
General informations
val get_lame_version : unit -> string
Get the lame version number.
val get_lame_short_version : unit -> string
Get the lame version number (shorter than get_lame_version
).
val get_lame_very_short_version : unit -> string
Get the lame version number (shorter than get_lame_short_version
).
val get_lame_url : unit -> string
Get the url of the lame website.
val get_psy_version : unit -> string
Get the version of the psy model.
Encoders
type
encoder
Type for lame encoders.
val create_encoder : unit -> encoder
Create a new lame encoder.
Parameters
val set_in_samplerate : encoder -> int -> unit
Input sample rate in Hz (default: 44100).
val set_num_channels : encoder -> int -> unit
Number of channels in input stream (default: 2).
val set_out_samplerate : encoder -> int -> unit
Output sample rate in Hz (default: 0, which means LAME picks best value
based on the amount of compression). MPEG only allows:
- MPEG1 (32, 44.1, 48 kHz)
- MPEG2 (16, 22.05, 24 kHz)
- MPEG2.5 (8, 11.025, 12 kHz)
val set_quality : encoder -> int -> unit
Internal algorithm selection. True quality is determined by the bitrate
but this variable will effect quality by selecting expensive or cheap
algorithms. The quality is an integer between 0 and 9, where 0=best (very
slow) and 9=worst. More precisely:
- 2: near-best quality, not too slow (recommended)
- 5: good quality, fast
- 7: ok quality, really fast
type
mode =
| |
Stereo |
| |
Joint_stereo |
| |
Dual_channel |
| |
Mono |
Compression mode.
val set_mode : encoder -> mode -> unit
Set the compression mode.
type
vbr_mode =
| |
Vbr_off |
| |
Vbr_rh |
| |
Vbr_abr |
| |
Vbr_mtrh |
| |
Vbr_max_indicator |
VBR (Variable BitRate) mode.
val set_vbr_mode : encoder -> vbr_mode -> unit
Set the VBR mode.
val set_vbr_quality : encoder -> int -> unit
Set the VBR quality level (0:highest, 9: lowest).
val set_vbr_mean_bitrate : encoder -> int -> unit
Set the VBR mean birate in kbps. Only used by Vbr_abr
mode.
val set_vbr_min_bitrate : encoder -> int -> unit
Set the minimal VBR bitrate in kbps.
val set_vbr_max_bitrate : encoder -> int -> unit
Set the maximal VBR bitrate in kbps.
val set_vbr_hard_min : encoder -> bool -> unit
If true
, enforce the minimal VBR bitrate. Normally it will be violated
for analog silence.
val set_brate : encoder -> int -> unit
Set the bitrate of compressed data. You can either set this or use
set_compression_ratio
.
val set_compression_ratio : encoder -> float -> unit
Set the compression ratio (default: 11).
exception Init_params_failed
A call to init_params
failed for some reason.
val init_params : encoder -> unit
Initialize lame's parameters. Should be called before encoding (and after
having set the parameters). Raises Init_params_failed
on error.
val init_bitstream : encoder -> unit
Write id3v2 and Xing headers into the front of the bitstream, and set
frame counters and bitrate histogram data to 0. Normally, this is called by
init_params
. You can call this after encode_flush_nogap
.
Encoding
exception Init_params_not_called
You should have called init_params
.
exception Psychoacoustic_problem
A problem occured with psychoacoustics.
exception Unknown_error of int
This should not have happened. Please report.
val encode_buffer_part : encoder -> string -> int -> int -> string
encode_buffer_part enc buf ofs smpl
encodes samples
samples (per channel) of buf
starting at position ofs
.
val encode_buffer : encoder -> string -> int -> string
Same as encode_buffer_part
but with ofs = 0
.
val encode_buffer_float_part : encoder -> float array -> float array -> int -> int -> string
encode_buffer_float_part enc left right ofs smpl
encodes samples
samples of left
and right
channels starting at position ofs
.
Floats are expected to range over -1;1
.
val encode_buffer_float : encoder -> float array -> float array -> int -> string
Same as encode_buffer_float_part
but with ofs = 0
.
val encode_flush : encoder -> string
Flush the PCM buffers, padding with zeros if needed to make a complete
frame. Will also write id3v1 tags (if any) into the bitstream.
val encode_flush_nogap : encoder -> string
Flush the PCM buffers, padding with zeros if needed to make a complete
frame. This function will not write id3v1 tags into the bitstream.
Id3 tags
module Id3tag: sig
.. end
Informations about encoding
type
mpeg_version =
| |
Mpeg_1 |
| |
Mpeg_2 |
| |
Mpeg_2_5 |
MPEG version.
val get_version : encoder -> mpeg_version
The MPEG version used by the encoder.
val get_encoder_delay : encoder -> int
Get the encoder delay.
val get_framesize : encoder -> int
Size of an mpeg frame in bytes.
val get_nb_samples_to_encode : encoder -> int
Number of PCM samples buffered, but not yet encoded to mp3 data.
val get_nb_encoded_frames : encoder -> int
Number of frames encoded so far.
val get_nb_frames : encoder -> int
Estimate of the total number of frames to be encoded
(only valid if set_nb_samples
was called).