Crash while encoding audio frame

[yunsun330]

I am trying to generate an audio frame for slient audio.

/* frame containing input raw audio */
AVFrame *audio_frame = av_frame_alloc();
if (!audio_frame) {
    return NO;
}

audio_frame->nb_samples     = audio_out_stream->codec->frame_size;
audio_frame->format         = audio_out_stream->codec->sample_fmt;
audio_frame->channel_layout = audio_out_stream->codec->channel_layout;

/* the codec gives us the frame size, in samples,
 * we calculate the size of the samples buffer in bytes */
int buffer_size = av_samples_get_buffer_size(NULL,
                                             audio_out_stream->codec->channels,
                                             audio_out_stream->codec->frame_size,
                                             audio_out_stream->codec->sample_fmt, 0);
if (buffer_size < 0) {
    return NO;
}

uint16_t *samples = av_malloc(buffer_size);
memset(samples, 0, buffer_size);

/* setup the data pointers in the AVFrame */
if (avcodec_fill_audio_frame(audio_frame,
                             audio_out_stream->codec->channels,
                             audio_out_stream->codec->sample_fmt,
                             (const uint8_t*)samples, buffer_size, 0) < 0) {
    return NO;
}

/* encode a single tone sound */
    AVPacket packet;

    av_init_packet(&packet);
    packet.data = NULL; // packet data will be allocated by the encoder
    packet.size = 0;

    /* encode the samples */
    int got_output;
    if (avcodec_encode_audio2(audio_out_stream->codec, &packet, audio_frame, &got_output) < 0) {
        return NO;
    }
    if (got_output) {
        packet.pts = 30*numPacketsSent;
        numPacketsSent++;

        int res = av_write_frame(ofmt_ctx, &packet);
        if (res < 0) {
            return NO;
        }
    }
}
av_frame_free(&audio_frame);

And, I am getting crash in avcodec_encode_audio2 function.
Can you please let me know what's wrong here?