+static av_cold int libgsm_decode_init(AVCodecContext *avctx) {
+ if (avctx->channels > 1) {
+ av_log(avctx, AV_LOG_ERROR, "Mono required for GSM, got %d channels\n",
+ avctx->channels);
+ return -1;
+ }
+
+ if (!avctx->channels)
+ avctx->channels = 1;
+
+ if (!avctx->sample_rate)
+ avctx->sample_rate = 8000;
+
+ avctx->sample_fmt = AV_SAMPLE_FMT_S16;
+
+ avctx->priv_data = gsm_create();
+
+ switch(avctx->codec_id) {
+ case CODEC_ID_GSM:
+ avctx->frame_size = GSM_FRAME_SIZE;
+ avctx->block_align = GSM_BLOCK_SIZE;
+ break;
+ case CODEC_ID_GSM_MS: {
+ int one = 1;
+ gsm_option(avctx->priv_data, GSM_OPT_WAV49, &one);
+ avctx->frame_size = 2 * GSM_FRAME_SIZE;
+ avctx->block_align = GSM_MS_BLOCK_SIZE;
+ }
+ }
+
+ return 0;
+}
+
+static av_cold int libgsm_decode_close(AVCodecContext *avctx) {
+ gsm_destroy(avctx->priv_data);
+ avctx->priv_data = NULL;
+ return 0;
+}
+