if (s->first_frame) s->first_frame = num = 0;
int MP3lame_encode_frame(AVCodecContext *avctx,                     unsigned char *frame, int buf_size, void *data){	Mp3AudioContext *s = avctx->priv_data;	int num;	/* lame 3.91 dies on '1-channel interleaved' data */	if (s->stereo) {		num = lame_encode_buffer_interleaved(s->gfp, data,			MPA_FRAME_SIZE, frame, buf_size);	} else {		num = lame_encode_buffer(s->gfp, data, data, MPA_FRAME_SIZE,			frame, buf_size);	}	/* lame 3.91 outputs the first frame as garbage */	if (s->first_frame)		s->first_frame = num = 0;	return num;}