blob: 455f175464153f15c066c0f113510167ff8284c7 [file] [log] [blame]
/*
* Copyright (c) 2012 The WebRTC project authors. All Rights Reserved.
*
* Use of this source code is governed by a BSD-style license
* that can be found in the LICENSE file in the root of the source
* tree. An additional intellectual property rights grant can be found
* in the file PATENTS. All contributing project authors may
* be found in the AUTHORS file in the root of the source tree.
*/
#include "modules/audio_coding/codecs/opus/opus_interface.h"
#include <cstdlib>
#include "rtc_base/checks.h"
#include "system_wrappers/include/field_trial.h"
enum {
#if WEBRTC_OPUS_SUPPORT_120MS_PTIME
/* Maximum supported frame size in WebRTC is 120 ms. */
kWebRtcOpusMaxEncodeFrameSizeMs = 120,
#else
/* Maximum supported frame size in WebRTC is 60 ms. */
kWebRtcOpusMaxEncodeFrameSizeMs = 60,
#endif
/* The format allows up to 120 ms frames. Since we don't control the other
* side, we must allow for packets of that size. NetEq is currently limited
* to 60 ms on the receive side. */
kWebRtcOpusMaxDecodeFrameSizeMs = 120,
// Duration of audio that each call to packet loss concealment covers.
kWebRtcOpusPlcFrameSizeMs = 10,
};
constexpr char kPlcUsePrevDecodedSamplesFieldTrial[] =
"WebRTC-Audio-OpusPlcUsePrevDecodedSamples";
static int FrameSizePerChannel(int frame_size_ms, int sample_rate_hz) {
RTC_DCHECK_GT(frame_size_ms, 0);
RTC_DCHECK_EQ(frame_size_ms % 10, 0);
RTC_DCHECK_GT(sample_rate_hz, 0);
RTC_DCHECK_EQ(sample_rate_hz % 1000, 0);
return frame_size_ms * (sample_rate_hz / 1000);
}
// Maximum sample count per channel.
static int MaxFrameSizePerChannel(int sample_rate_hz) {
return FrameSizePerChannel(kWebRtcOpusMaxDecodeFrameSizeMs, sample_rate_hz);
}
// Default sample count per channel.
static int DefaultFrameSizePerChannel(int sample_rate_hz) {
return FrameSizePerChannel(20, sample_rate_hz);
}
int16_t WebRtcOpus_EncoderCreate(OpusEncInst** inst,
size_t channels,
int32_t application,
int sample_rate_hz) {
int opus_app;
if (!inst)
return -1;
switch (application) {
case 0:
opus_app = OPUS_APPLICATION_VOIP;
break;
case 1:
opus_app = OPUS_APPLICATION_AUDIO;
break;
default:
return -1;
}
OpusEncInst* state =
reinterpret_cast<OpusEncInst*>(calloc(1, sizeof(OpusEncInst)));
RTC_DCHECK(state);
int error;
state->encoder = opus_encoder_create(
sample_rate_hz, static_cast<int>(channels), opus_app, &error);
if (error != OPUS_OK || (!state->encoder && !state->multistream_encoder)) {
WebRtcOpus_EncoderFree(state);
return -1;
}
state->in_dtx_mode = 0;
state->channels = channels;
*inst = state;
return 0;
}
int16_t WebRtcOpus_MultistreamEncoderCreate(
OpusEncInst** inst,
size_t channels,
int32_t application,
size_t streams,
size_t coupled_streams,
const unsigned char* channel_mapping) {
int opus_app;
if (!inst)
return -1;
switch (application) {
case 0:
opus_app = OPUS_APPLICATION_VOIP;
break;
case 1:
opus_app = OPUS_APPLICATION_AUDIO;
break;
default:
return -1;
}
OpusEncInst* state =
reinterpret_cast<OpusEncInst*>(calloc(1, sizeof(OpusEncInst)));
RTC_DCHECK(state);
int error;
state->multistream_encoder =
opus_multistream_encoder_create(48000, channels, streams, coupled_streams,
channel_mapping, opus_app, &error);
if (error != OPUS_OK || (!state->encoder && !state->multistream_encoder)) {
WebRtcOpus_EncoderFree(state);
return -1;
}
state->in_dtx_mode = 0;
state->channels = channels;
*inst = state;
return 0;
}
int16_t WebRtcOpus_EncoderFree(OpusEncInst* inst) {
if (inst) {
if (inst->encoder) {
opus_encoder_destroy(inst->encoder);
} else {
opus_multistream_encoder_destroy(inst->multistream_encoder);
}
free(inst);
return 0;
} else {
return -1;
}
}
int WebRtcOpus_Encode(OpusEncInst* inst,
const int16_t* audio_in,
size_t samples,
size_t length_encoded_buffer,
uint8_t* encoded) {
int res;
if (samples > 48 * kWebRtcOpusMaxEncodeFrameSizeMs) {
return -1;
}
if (inst->encoder) {
res = opus_encode(inst->encoder, (const opus_int16*)audio_in,
static_cast<int>(samples), encoded,
static_cast<opus_int32>(length_encoded_buffer));
} else {
res = opus_multistream_encode(
inst->multistream_encoder, (const opus_int16*)audio_in,
static_cast<int>(samples), encoded,
static_cast<opus_int32>(length_encoded_buffer));
}
if (res <= 0) {
return -1;
}
if (res <= 2) {
// Indicates DTX since the packet has nothing but a header. In principle,
// there is no need to send this packet. However, we do transmit the first
// occurrence to let the decoder know that the encoder enters DTX mode.
if (inst->in_dtx_mode) {
return 0;
} else {
inst->in_dtx_mode = 1;
return res;
}
}
inst->in_dtx_mode = 0;
return res;
}
#define ENCODER_CTL(inst, vargs) \
(inst->encoder \
? opus_encoder_ctl(inst->encoder, vargs) \
: opus_multistream_encoder_ctl(inst->multistream_encoder, vargs))
int16_t WebRtcOpus_SetBitRate(OpusEncInst* inst, int32_t rate) {
if (inst) {
return ENCODER_CTL(inst, OPUS_SET_BITRATE(rate));
} else {
return -1;
}
}
int16_t WebRtcOpus_SetPacketLossRate(OpusEncInst* inst, int32_t loss_rate) {
if (inst) {
return ENCODER_CTL(inst, OPUS_SET_PACKET_LOSS_PERC(loss_rate));
} else {
return -1;
}
}
int16_t WebRtcOpus_SetMaxPlaybackRate(OpusEncInst* inst, int32_t frequency_hz) {
opus_int32 set_bandwidth;
if (!inst)
return -1;
if (frequency_hz <= 8000) {
set_bandwidth = OPUS_BANDWIDTH_NARROWBAND;
} else if (frequency_hz <= 12000) {
set_bandwidth = OPUS_BANDWIDTH_MEDIUMBAND;
} else if (frequency_hz <= 16000) {
set_bandwidth = OPUS_BANDWIDTH_WIDEBAND;
} else if (frequency_hz <= 24000) {
set_bandwidth = OPUS_BANDWIDTH_SUPERWIDEBAND;
} else {
set_bandwidth = OPUS_BANDWIDTH_FULLBAND;
}
return ENCODER_CTL(inst, OPUS_SET_MAX_BANDWIDTH(set_bandwidth));
}
int16_t WebRtcOpus_GetMaxPlaybackRate(OpusEncInst* const inst,
int32_t* result_hz) {
if (inst->encoder) {
if (opus_encoder_ctl(inst->encoder, OPUS_GET_MAX_BANDWIDTH(result_hz)) ==
OPUS_OK) {
return 0;
}
return -1;
}
opus_int32 max_bandwidth;
int s;
int ret;
max_bandwidth = 0;
ret = OPUS_OK;
s = 0;
while (ret == OPUS_OK) {
OpusEncoder* enc;
opus_int32 bandwidth;
ret = ENCODER_CTL(inst, OPUS_MULTISTREAM_GET_ENCODER_STATE(s, &enc));
if (ret == OPUS_BAD_ARG)
break;
if (ret != OPUS_OK)
return -1;
if (opus_encoder_ctl(enc, OPUS_GET_MAX_BANDWIDTH(&bandwidth)) != OPUS_OK)
return -1;
if (max_bandwidth != 0 && max_bandwidth != bandwidth)
return -1;
max_bandwidth = bandwidth;
s++;
}
*result_hz = max_bandwidth;
return 0;
}
int16_t WebRtcOpus_EnableFec(OpusEncInst* inst) {
if (inst) {
return ENCODER_CTL(inst, OPUS_SET_INBAND_FEC(1));
} else {
return -1;
}
}
int16_t WebRtcOpus_DisableFec(OpusEncInst* inst) {
if (inst) {
return ENCODER_CTL(inst, OPUS_SET_INBAND_FEC(0));
} else {
return -1;
}
}
int16_t WebRtcOpus_EnableDtx(OpusEncInst* inst) {
if (!inst) {
return -1;
}
// To prevent Opus from entering CELT-only mode by forcing signal type to
// voice to make sure that DTX behaves correctly. Currently, DTX does not
// last long during a pure silence, if the signal type is not forced.
// TODO(minyue): Remove the signal type forcing when Opus DTX works properly
// without it.
int ret = ENCODER_CTL(inst, OPUS_SET_SIGNAL(OPUS_SIGNAL_VOICE));
if (ret != OPUS_OK)
return ret;
return ENCODER_CTL(inst, OPUS_SET_DTX(1));
}
int16_t WebRtcOpus_DisableDtx(OpusEncInst* inst) {
if (inst) {
int ret = ENCODER_CTL(inst, OPUS_SET_SIGNAL(OPUS_AUTO));
if (ret != OPUS_OK)
return ret;
return ENCODER_CTL(inst, OPUS_SET_DTX(0));
} else {
return -1;
}
}
int16_t WebRtcOpus_EnableCbr(OpusEncInst* inst) {
if (inst) {
return ENCODER_CTL(inst, OPUS_SET_VBR(0));
} else {
return -1;
}
}
int16_t WebRtcOpus_DisableCbr(OpusEncInst* inst) {
if (inst) {
return ENCODER_CTL(inst, OPUS_SET_VBR(1));
} else {
return -1;
}
}
int16_t WebRtcOpus_SetComplexity(OpusEncInst* inst, int32_t complexity) {
if (inst) {
return ENCODER_CTL(inst, OPUS_SET_COMPLEXITY(complexity));
} else {
return -1;
}
}
int32_t WebRtcOpus_GetBandwidth(OpusEncInst* inst) {
if (!inst) {
return -1;
}
int32_t bandwidth;
if (ENCODER_CTL(inst, OPUS_GET_BANDWIDTH(&bandwidth)) == 0) {
return bandwidth;
} else {
return -1;
}
}
int16_t WebRtcOpus_SetBandwidth(OpusEncInst* inst, int32_t bandwidth) {
if (inst) {
return ENCODER_CTL(inst, OPUS_SET_BANDWIDTH(bandwidth));
} else {
return -1;
}
}
int16_t WebRtcOpus_SetForceChannels(OpusEncInst* inst, size_t num_channels) {
if (!inst)
return -1;
if (num_channels == 0) {
return ENCODER_CTL(inst, OPUS_SET_FORCE_CHANNELS(OPUS_AUTO));
} else if (num_channels == 1 || num_channels == 2) {
return ENCODER_CTL(inst, OPUS_SET_FORCE_CHANNELS(num_channels));
} else {
return -1;
}
}
int32_t WebRtcOpus_GetInDtx(OpusEncInst* inst) {
if (!inst) {
return -1;
}
#ifdef OPUS_GET_IN_DTX
int32_t in_dtx;
if (ENCODER_CTL(inst, OPUS_GET_IN_DTX(&in_dtx)) == 0) {
return in_dtx;
}
#endif
return -1;
}
int16_t WebRtcOpus_DecoderCreate(OpusDecInst** inst,
size_t channels,
int sample_rate_hz) {
int error;
OpusDecInst* state;
if (inst != NULL) {
// Create Opus decoder state.
state = reinterpret_cast<OpusDecInst*>(calloc(1, sizeof(OpusDecInst)));
if (state == NULL) {
return -1;
}
state->decoder =
opus_decoder_create(sample_rate_hz, static_cast<int>(channels), &error);
if (error == OPUS_OK && state->decoder) {
// Creation of memory all ok.
state->channels = channels;
state->sample_rate_hz = sample_rate_hz;
state->plc_use_prev_decoded_samples =
webrtc::field_trial::IsEnabled(kPlcUsePrevDecodedSamplesFieldTrial);
if (state->plc_use_prev_decoded_samples) {
state->prev_decoded_samples =
DefaultFrameSizePerChannel(state->sample_rate_hz);
}
state->in_dtx_mode = 0;
*inst = state;
return 0;
}
// If memory allocation was unsuccessful, free the entire state.
if (state->decoder) {
opus_decoder_destroy(state->decoder);
}
free(state);
}
return -1;
}
int16_t WebRtcOpus_MultistreamDecoderCreate(
OpusDecInst** inst,
size_t channels,
size_t streams,
size_t coupled_streams,
const unsigned char* channel_mapping) {
int error;
OpusDecInst* state;
if (inst != NULL) {
// Create Opus decoder state.
state = reinterpret_cast<OpusDecInst*>(calloc(1, sizeof(OpusDecInst)));
if (state == NULL) {
return -1;
}
// Create new memory, always at 48000 Hz.
state->multistream_decoder = opus_multistream_decoder_create(
48000, channels, streams, coupled_streams, channel_mapping, &error);
if (error == OPUS_OK && state->multistream_decoder) {
// Creation of memory all ok.
state->channels = channels;
state->sample_rate_hz = 48000;
state->plc_use_prev_decoded_samples =
webrtc::field_trial::IsEnabled(kPlcUsePrevDecodedSamplesFieldTrial);
if (state->plc_use_prev_decoded_samples) {
state->prev_decoded_samples =
DefaultFrameSizePerChannel(state->sample_rate_hz);
}
state->in_dtx_mode = 0;
*inst = state;
return 0;
}
// If memory allocation was unsuccessful, free the entire state.
opus_multistream_decoder_destroy(state->multistream_decoder);
free(state);
}
return -1;
}
int16_t WebRtcOpus_DecoderFree(OpusDecInst* inst) {
if (inst) {
if (inst->decoder) {
opus_decoder_destroy(inst->decoder);
} else if (inst->multistream_decoder) {
opus_multistream_decoder_destroy(inst->multistream_decoder);
}
free(inst);
return 0;
} else {
return -1;
}
}
size_t WebRtcOpus_DecoderChannels(OpusDecInst* inst) {
return inst->channels;
}
void WebRtcOpus_DecoderInit(OpusDecInst* inst) {
if (inst->decoder) {
opus_decoder_ctl(inst->decoder, OPUS_RESET_STATE);
} else {
opus_multistream_decoder_ctl(inst->multistream_decoder, OPUS_RESET_STATE);
}
inst->in_dtx_mode = 0;
}
/* For decoder to determine if it is to output speech or comfort noise. */
static int16_t DetermineAudioType(OpusDecInst* inst, size_t encoded_bytes) {
// Audio type becomes comfort noise if |encoded_byte| is 1 and keeps
// to be so if the following |encoded_byte| are 0 or 1.
if (encoded_bytes == 0 && inst->in_dtx_mode) {
return 2; // Comfort noise.
} else if (encoded_bytes == 1 || encoded_bytes == 2) {
// TODO(henrik.lundin): There is a slight risk that a 2-byte payload is in
// fact a 1-byte TOC with a 1-byte payload. That will be erroneously
// interpreted as comfort noise output, but such a payload is probably
// faulty anyway.
// TODO(webrtc:10218): This is wrong for multistream opus. Then are several
// single-stream packets glued together with some packet size bytes in
// between. See https://tools.ietf.org/html/rfc6716#appendix-B
inst->in_dtx_mode = 1;
return 2; // Comfort noise.
} else {
inst->in_dtx_mode = 0;
return 0; // Speech.
}
}
/* |frame_size| is set to maximum Opus frame size in the normal case, and
* is set to the number of samples needed for PLC in case of losses.
* It is up to the caller to make sure the value is correct. */
static int DecodeNative(OpusDecInst* inst,
const uint8_t* encoded,
size_t encoded_bytes,
int frame_size,
int16_t* decoded,
int16_t* audio_type,
int decode_fec) {
int res = -1;
if (inst->decoder) {
res = opus_decode(
inst->decoder, encoded, static_cast<opus_int32>(encoded_bytes),
reinterpret_cast<opus_int16*>(decoded), frame_size, decode_fec);
} else {
res = opus_multistream_decode(inst->multistream_decoder, encoded,
static_cast<opus_int32>(encoded_bytes),
reinterpret_cast<opus_int16*>(decoded),
frame_size, decode_fec);
}
if (res <= 0)
return -1;
*audio_type = DetermineAudioType(inst, encoded_bytes);
return res;
}
static int DecodePlc(OpusDecInst* inst, int16_t* decoded) {
int16_t audio_type = 0;
int decoded_samples;
int plc_samples =
FrameSizePerChannel(kWebRtcOpusPlcFrameSizeMs, inst->sample_rate_hz);
if (inst->plc_use_prev_decoded_samples) {
/* The number of samples we ask for is |number_of_lost_frames| times
* |prev_decoded_samples_|. Limit the number of samples to maximum
* |MaxFrameSizePerChannel()|. */
plc_samples = inst->prev_decoded_samples;
const int max_samples_per_channel =
MaxFrameSizePerChannel(inst->sample_rate_hz);
plc_samples = plc_samples <= max_samples_per_channel
? plc_samples
: max_samples_per_channel;
}
decoded_samples =
DecodeNative(inst, NULL, 0, plc_samples, decoded, &audio_type, 0);
if (decoded_samples < 0) {
return -1;
}
return decoded_samples;
}
int WebRtcOpus_Decode(OpusDecInst* inst,
const uint8_t* encoded,
size_t encoded_bytes,
int16_t* decoded,
int16_t* audio_type) {
int decoded_samples;
if (encoded_bytes == 0) {
*audio_type = DetermineAudioType(inst, encoded_bytes);
decoded_samples = DecodePlc(inst, decoded);
} else {
decoded_samples = DecodeNative(inst, encoded, encoded_bytes,
MaxFrameSizePerChannel(inst->sample_rate_hz),
decoded, audio_type, 0);
}
if (decoded_samples < 0) {
return -1;
}
if (inst->plc_use_prev_decoded_samples) {
/* Update decoded sample memory, to be used by the PLC in case of losses. */
inst->prev_decoded_samples = decoded_samples;
}
return decoded_samples;
}
int WebRtcOpus_DecodeFec(OpusDecInst* inst,
const uint8_t* encoded,
size_t encoded_bytes,
int16_t* decoded,
int16_t* audio_type) {
int decoded_samples;
int fec_samples;
if (WebRtcOpus_PacketHasFec(encoded, encoded_bytes) != 1) {
return 0;
}
fec_samples =
opus_packet_get_samples_per_frame(encoded, inst->sample_rate_hz);
decoded_samples = DecodeNative(inst, encoded, encoded_bytes, fec_samples,
decoded, audio_type, 1);
if (decoded_samples < 0) {
return -1;
}
return decoded_samples;
}
int WebRtcOpus_DurationEst(OpusDecInst* inst,
const uint8_t* payload,
size_t payload_length_bytes) {
if (payload_length_bytes == 0) {
// WebRtcOpus_Decode calls PLC when payload length is zero. So we return
// PLC duration correspondingly.
return WebRtcOpus_PlcDuration(inst);
}
int frames, samples;
frames = opus_packet_get_nb_frames(
payload, static_cast<opus_int32>(payload_length_bytes));
if (frames < 0) {
/* Invalid payload data. */
return 0;
}
samples =
frames * opus_packet_get_samples_per_frame(payload, inst->sample_rate_hz);
if (samples > 120 * inst->sample_rate_hz / 1000) {
// More than 120 ms' worth of samples.
return 0;
}
return samples;
}
int WebRtcOpus_PlcDuration(OpusDecInst* inst) {
if (inst->plc_use_prev_decoded_samples) {
/* The number of samples we ask for is |number_of_lost_frames| times
* |prev_decoded_samples_|. Limit the number of samples to maximum
* |MaxFrameSizePerChannel()|. */
const int plc_samples = inst->prev_decoded_samples;
const int max_samples_per_channel =
MaxFrameSizePerChannel(inst->sample_rate_hz);
return plc_samples <= max_samples_per_channel ? plc_samples
: max_samples_per_channel;
}
return FrameSizePerChannel(kWebRtcOpusPlcFrameSizeMs, inst->sample_rate_hz);
}
int WebRtcOpus_FecDurationEst(const uint8_t* payload,
size_t payload_length_bytes,
int sample_rate_hz) {
if (WebRtcOpus_PacketHasFec(payload, payload_length_bytes) != 1) {
return 0;
}
const int samples =
opus_packet_get_samples_per_frame(payload, sample_rate_hz);
const int samples_per_ms = sample_rate_hz / 1000;
if (samples < 10 * samples_per_ms || samples > 120 * samples_per_ms) {
/* Invalid payload duration. */
return 0;
}
return samples;
}
int WebRtcOpus_NumSilkFrames(const uint8_t* payload) {
// For computing the payload length in ms, the sample rate is not important
// since it cancels out. We use 48 kHz, but any valid sample rate would work.
int payload_length_ms =
opus_packet_get_samples_per_frame(payload, 48000) / 48;
if (payload_length_ms < 10)
payload_length_ms = 10;
int silk_frames;
switch (payload_length_ms) {
case 10:
case 20:
silk_frames = 1;
break;
case 40:
silk_frames = 2;
break;
case 60:
silk_frames = 3;
break;
default:
return 0; // It is actually even an invalid packet.
}
return silk_frames;
}
// This method is based on Definition of the Opus Audio Codec
// (https://tools.ietf.org/html/rfc6716). Basically, this method is based on
// parsing the LP layer of an Opus packet, particularly the LBRR flag.
int WebRtcOpus_PacketHasFec(const uint8_t* payload,
size_t payload_length_bytes) {
if (payload == NULL || payload_length_bytes == 0)
return 0;
// In CELT_ONLY mode, packets should not have FEC.
if (payload[0] & 0x80)
return 0;
int silk_frames = WebRtcOpus_NumSilkFrames(payload);
if (silk_frames == 0)
return 0; // Not valid.
const int channels = opus_packet_get_nb_channels(payload);
RTC_DCHECK(channels == 1 || channels == 2);
// Max number of frames in an Opus packet is 48.
opus_int16 frame_sizes[48];
const unsigned char* frame_data[48];
// Parse packet to get the frames. But we only care about the first frame,
// since we can only decode the FEC from the first one.
if (opus_packet_parse(payload, static_cast<opus_int32>(payload_length_bytes),
NULL, frame_data, frame_sizes, NULL) < 0) {
return 0;
}
if (frame_sizes[0] < 1) {
return 0;
}
// A frame starts with the LP layer. The LP layer begins with two to eight
// header bits.These consist of one VAD bit per SILK frame (up to 3),
// followed by a single flag indicating the presence of LBRR frames.
// For a stereo packet, these first flags correspond to the mid channel, and
// a second set of flags is included for the side channel. Because these are
// the first symbols decoded by the range coder and because they are coded
// as binary values with uniform probability, they can be extracted directly
// from the most significant bits of the first byte of compressed data.
for (int n = 0; n < channels; n++) {
// The LBRR bit for channel 1 is on the (|silk_frames| + 1)-th bit, and
// that of channel 2 is on the |(|silk_frames| + 1) * 2 + 1|-th bit.
if (frame_data[0][0] & (0x80 >> ((n + 1) * (silk_frames + 1) - 1)))
return 1;
}
return 0;
}
int WebRtcOpus_PacketHasVoiceActivity(const uint8_t* payload,
size_t payload_length_bytes) {
if (payload == NULL || payload_length_bytes == 0)
return 0;
// In CELT_ONLY mode we can not determine whether there is VAD.
if (payload[0] & 0x80)
return -1;
int silk_frames = WebRtcOpus_NumSilkFrames(payload);
if (silk_frames == 0)
return 0;
const int channels = opus_packet_get_nb_channels(payload);
RTC_DCHECK(channels == 1 || channels == 2);
// Max number of frames in an Opus packet is 48.
opus_int16 frame_sizes[48];
const unsigned char* frame_data[48];
// Parse packet to get the frames.
int frames =
opus_packet_parse(payload, static_cast<opus_int32>(payload_length_bytes),
NULL, frame_data, frame_sizes, NULL);
if (frames < 0)
return -1;
// Iterate over all Opus frames which may contain multiple SILK frames.
for (int frame = 0; frame < frames; frame++) {
if (frame_sizes[frame] < 1) {
continue;
}
if (frame_data[frame][0] >> (8 - silk_frames))
return 1;
if (channels == 2 &&
(frame_data[frame][0] << (silk_frames + 1)) >> (8 - silk_frames))
return 1;
}
return 0;
}