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[lwip-users] Error-"Incompatible Types"

From: Teckinal Greek
Subject: [lwip-users] Error-"Incompatible Types"
Date: Fri, 26 Nov 2010 13:51:15 +0000

Hi all,
I am planning to implement RTP on lwIP in that means I am compressing the PCM data using a self written audio codec. 

For this I am using this piece of code to convert the data from Analog to Digital i.e to PCM[some functions are inbuilt functions on my Board]

int16_t pcm_buffer[1024] = {0};

void audio(void)
    int i, j;
    audio = audio_open(AUDIO_1);
    while (1)
        get_audio(pcm_buf, 1024);


int get_audio(short *buffer, int n)
    int s;

        s = audio_record(audio, buffer, n);
        n -= s;
        buffer += s;
    }while (n != 0);

    return s;

What I am assuming here is that the PCM data is stored in the buffer "pcm_buffer" and it is of int 16 bit.

My encoder code goes like this ....

unsigned char linear2alaw(int pcm_val) /*here we expect pcm_val to be 2's compliment which is of 16-bit-range */
    int sign, exponent, expMask, mantissa;
    unsigned char alaw;

   return (unsigned char)(alaw^0xD5);

In my RTP part of my code I need to put this compressed data on to a send buffer which is declared like  this......

#define RTP_PACKET_SIZE = 1500
static uint8_t rtp_send_packet[RTP_PACKET_SIZE];

Now I call the linear2alaw function pass the pcm value and again again the returned value to rtp_send_packet[] buffer like this.......

static uint8_t rtp_send_packet[RTP_PACKET_SIZE] = linear2alaw(stereo_buf);

When I compile my code it throws an error saying "incompatible types".

On the other hand if I assign this in another way like.......

static uint8_t rtp_send_packet[RTP_PACKET_SIZE] ;

rtp_send_packet[RTP_PACKET_SIZE] = linear2alaw(stereo_buf);

then it throws another error like ........"rtp_send_packet" redeclared with a different type"

Can anybody find out where am I making mistake. I am using lwIP TCP/IP stack for my implementation.


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