1/*
2 * Copyright (c) 2001 Fabrice Bellard
3 *
4 * Permission is hereby granted, free of charge, to any person obtaining a copy
5 * of this software and associated documentation files (the "Software"), to deal
6 * in the Software without restriction, including without limitation the rights
7 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
8 * copies of the Software, and to permit persons to whom the Software is
9 * furnished to do so, subject to the following conditions:
10 *
11 * The above copyright notice and this permission notice shall be included in
12 * all copies or substantial portions of the Software.
13 *
14 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
15 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
16 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
17 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
18 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
19 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
20 * THE SOFTWARE.
21 */
22
23/**
24 * @file
25 * audio encoding with libavcodec API example.
26 *
27 * @example encode_audio.c
28 */
29
30#include <stdint.h>
31#include <stdio.h>
32#include <stdlib.h>
33
34#include <libavcodec/avcodec.h>
35
36#include <libavutil/channel_layout.h>
37#include <libavutil/common.h>
38#include <libavutil/frame.h>
39#include <libavutil/samplefmt.h>
40
41/* check that a given sample format is supported by the encoder */
42static int check_sample_fmt(const AVCodec *codec, enum AVSampleFormat sample_fmt)
43{
44    const enum AVSampleFormat *p = codec->sample_fmts;
45
46    while (*p != AV_SAMPLE_FMT_NONE) {
47        if (*p == sample_fmt)
48            return 1;
49        p++;
50    }
51    return 0;
52}
53
54/* just pick the highest supported samplerate */
55static int select_sample_rate(const AVCodec *codec)
56{
57    const int *p;
58    int best_samplerate = 0;
59
60    if (!codec->supported_samplerates)
61        return 44100;
62
63    p = codec->supported_samplerates;
64    while (*p) {
65        if (!best_samplerate || abs(44100 - *p) < abs(44100 - best_samplerate))
66            best_samplerate = *p;
67        p++;
68    }
69    return best_samplerate;
70}
71
72/* select layout with the highest channel count */
73static int select_channel_layout(const AVCodec *codec, AVChannelLayout *dst)
74{
75    const AVChannelLayout *p, *best_ch_layout;
76    int best_nb_channels   = 0;
77
78    if (!codec->ch_layouts)
79        return av_channel_layout_copy(dst, &(AVChannelLayout)AV_CHANNEL_LAYOUT_STEREO);
80
81    p = codec->ch_layouts;
82    while (p->nb_channels) {
83        int nb_channels = p->nb_channels;
84
85        if (nb_channels > best_nb_channels) {
86            best_ch_layout   = p;
87            best_nb_channels = nb_channels;
88        }
89        p++;
90    }
91    return av_channel_layout_copy(dst, best_ch_layout);
92}
93
94static void encode(AVCodecContext *ctx, AVFrame *frame, AVPacket *pkt,
95                   FILE *output)
96{
97    int ret;
98
99    /* send the frame for encoding */
100    ret = avcodec_send_frame(ctx, frame);
101    if (ret < 0) {
102        fprintf(stderr, "Error sending the frame to the encoder\n");
103        exit(1);
104    }
105
106    /* read all the available output packets (in general there may be any
107     * number of them */
108    while (ret >= 0) {
109        ret = avcodec_receive_packet(ctx, pkt);
110        if (ret == AVERROR(EAGAIN) || ret == AVERROR_EOF)
111            return;
112        else if (ret < 0) {
113            fprintf(stderr, "Error encoding audio frame\n");
114            exit(1);
115        }
116
117        fwrite(pkt->data, 1, pkt->size, output);
118        av_packet_unref(pkt);
119    }
120}
121
122int main(int argc, char **argv)
123{
124    const char *filename;
125    const AVCodec *codec;
126    AVCodecContext *c= NULL;
127    AVFrame *frame;
128    AVPacket *pkt;
129    int i, j, k, ret;
130    FILE *f;
131    uint16_t *samples;
132    float t, tincr;
133
134    if (argc <= 1) {
135        fprintf(stderr, "Usage: %s <output file>\n", argv[0]);
136        return 0;
137    }
138    filename = argv[1];
139
140    /* find the MP2 encoder */
141    codec = avcodec_find_encoder(AV_CODEC_ID_MP2);
142    if (!codec) {
143        fprintf(stderr, "Codec not found\n");
144        exit(1);
145    }
146
147    c = avcodec_alloc_context3(codec);
148    if (!c) {
149        fprintf(stderr, "Could not allocate audio codec context\n");
150        exit(1);
151    }
152
153    /* put sample parameters */
154    c->bit_rate = 64000;
155
156    /* check that the encoder supports s16 pcm input */
157    c->sample_fmt = AV_SAMPLE_FMT_S16;
158    if (!check_sample_fmt(codec, c->sample_fmt)) {
159        fprintf(stderr, "Encoder does not support sample format %s",
160                av_get_sample_fmt_name(c->sample_fmt));
161        exit(1);
162    }
163
164    /* select other audio parameters supported by the encoder */
165    c->sample_rate    = select_sample_rate(codec);
166    ret = select_channel_layout(codec, &c->ch_layout);
167    if (ret < 0)
168        exit(1);
169
170    /* open it */
171    if (avcodec_open2(c, codec, NULL) < 0) {
172        fprintf(stderr, "Could not open codec\n");
173        exit(1);
174    }
175
176    f = fopen(filename, "wb");
177    if (!f) {
178        fprintf(stderr, "Could not open %s\n", filename);
179        exit(1);
180    }
181
182    /* packet for holding encoded output */
183    pkt = av_packet_alloc();
184    if (!pkt) {
185        fprintf(stderr, "could not allocate the packet\n");
186        exit(1);
187    }
188
189    /* frame containing input raw audio */
190    frame = av_frame_alloc();
191    if (!frame) {
192        fprintf(stderr, "Could not allocate audio frame\n");
193        exit(1);
194    }
195
196    frame->nb_samples     = c->frame_size;
197    frame->format         = c->sample_fmt;
198    ret = av_channel_layout_copy(&frame->ch_layout, &c->ch_layout);
199    if (ret < 0)
200        exit(1);
201
202    /* allocate the data buffers */
203    ret = av_frame_get_buffer(frame, 0);
204    if (ret < 0) {
205        fprintf(stderr, "Could not allocate audio data buffers\n");
206        exit(1);
207    }
208
209    /* encode a single tone sound */
210    t = 0;
211    tincr = 2 * M_PI * 440.0 / c->sample_rate;
212    for (i = 0; i < 200; i++) {
213        /* make sure the frame is writable -- makes a copy if the encoder
214         * kept a reference internally */
215        ret = av_frame_make_writable(frame);
216        if (ret < 0)
217            exit(1);
218        samples = (uint16_t*)frame->data[0];
219
220        for (j = 0; j < c->frame_size; j++) {
221            samples[2*j] = (int)(sin(t) * 10000);
222
223            for (k = 1; k < c->ch_layout.nb_channels; k++)
224                samples[2*j + k] = samples[2*j];
225            t += tincr;
226        }
227        encode(c, frame, pkt, f);
228    }
229
230    /* flush the encoder */
231    encode(c, NULL, pkt, f);
232
233    fclose(f);
234
235    av_frame_free(&frame);
236    av_packet_free(&pkt);
237    avcodec_free_context(&c);
238
239    return 0;
240}
241