static void audio_encode_example(const char *filename) { AVCodec *codec; AVCodecContext *c= NULL; AVFrame *frame; AVPacket pkt; int i, j, k, ret, got_output; int buffer_size; FILE *f; uint16_t *samples; float t, tincr; printf("Encode audio file %s\n", filename); /* find the MP2 encoder */ codec = avcodec_find_encoder(AV_CODEC_ID_MP2); if (!codec) { fprintf(stderr, "Codec not found\n"); exit(1); } c = avcodec_alloc_context3(codec); if (!c) { fprintf(stderr, "Could not allocate audio codec context\n"); exit(1); } /* put sample parameters */ c->bit_rate = 64000; /* check that the encoder supports s16 pcm input */ c->sample_fmt = AV_SAMPLE_FMT_S16; if (!check_sample_fmt(codec, c->sample_fmt)) { fprintf(stderr, "Encoder does not support sample format %s", av_get_sample_fmt_name(c->sample_fmt)); exit(1); } /* select other audio parameters supported by the encoder */ c->sample_rate = select_sample_rate(codec); c->channel_layout = select_channel_layout(codec); c->channels = av_get_channel_layout_nb_channels(c->channel_layout); /* open it */ if (avcodec_open2(c, codec, NULL) < 0) { fprintf(stderr, "Could not open codec\n"); exit(1); } f = fopen(filename, "wb"); if (!f) { fprintf(stderr, "Could not open %s\n", filename); exit(1); } /* frame containing input raw audio */ frame = av_frame_alloc(); if (!frame) { fprintf(stderr, "Could not allocate audio frame\n"); exit(1); } frame->nb_samples = c->frame_size; frame->format = c->sample_fmt; frame->channel_layout = c->channel_layout; /* the codec gives us the frame size, in samples, * we calculate the size of the samples buffer in bytes */ buffer_size = av_samples_get_buffer_size(NULL, c->channels, c->frame_size, c->sample_fmt, 0); if (!buffer_size) { fprintf(stderr, "Could not get sample buffer size\n"); exit(1); } samples = av_malloc(buffer_size); if (!samples) { fprintf(stderr, "Could not allocate %d bytes for samples buffer\n", buffer_size); exit(1); } /* setup the data pointers in the AVFrame */ ret = avcodec_fill_audio_frame(frame, c->channels, c->sample_fmt, (const uint8_t*)samples, buffer_size, 0); if (ret < 0) { fprintf(stderr, "Could not setup audio frame\n"); exit(1); } /* encode a single tone sound */ t = 0; tincr = 2 * M_PI * 440.0 / c->sample_rate; for(i=0;i<200;i++) { av_init_packet(&pkt); pkt.data = NULL; // packet data will be allocated by the encoder pkt.size = 0; for (j = 0; j < c->frame_size; j++) { samples[2*j] = (int)(sin(t) * 10000); for (k = 1; k < c->channels; k++) samples[2*j + k] = samples[2*j]; t += tincr; } /* encode the samples */ ret = avcodec_encode_audio2(c, &pkt, frame, &got_output); if (ret < 0) { fprintf(stderr, "Error encoding audio frame\n"); exit(1); } if (got_output) { fwrite(pkt.data, 1, pkt.size, f); av_free_packet(&pkt); } } /* get the delayed frames */ for (got_output = 1; got_output; i++) { ret = avcodec_encode_audio2(c, &pkt, NULL, &got_output); if (ret < 0) { fprintf(stderr, "Error encoding frame\n"); exit(1); } if (got_output) { fwrite(pkt.data, 1, pkt.size, f); av_free_packet(&pkt); } } fclose(f); av_freep(&samples); av_frame_free(&frame); avcodec_close(c); av_free(c); }