ogg dev - Apr 2008 - More trival questions

Hopefullly this is once again something trivial I'm missing. I'm still
trying to figure out how to pull a part a stream. I get two out the three theora
headers I can see in the file (http://v2v.cc/~j/theora_testsuite/320x240.ogg) if
I use the buffer in the page struct and nothing usable if I try to use the
packet structs. Hopefully this is once again something something trivial
I've missed in the documentation.

Neil
>>>
#include <stdio.h>

#include "ogg/ogg.h"

#define BUF_SIZE 4096

int magic_check( unsigned char test, oggpack_buffer* buffer) {
        return (long) test == oggpack_read(buffer, 8);
}

void send_to_my_decoder(unsigned char *body, long body_len) {
        oggpack_buffer buffer;
        long bits_read;

        oggpack_readinit(&buffer, body, body_len);

        bits_read = oggpack_read(&buffer, 8);
        if ( bits_read == 0x80 || bits_read == 0x81 || bits_read == 0x82 ) {

                if ( magic_check( 't', &buffer) &&
                     magic_check( 'h', &buffer) &&
                     magic_check( 'e', &buffer) &&
                     magic_check( 'o', &buffer) &&
                     magic_check( 'r', &buffer) &&
                     magic_check( 'a', &buffer) ) {
                        printf("Magic!\n");
                }
                else {
                        printf("no Magic!\n");
                }
        }
        else {
                printf("not a header\n");
        }
}

int main( int argc, char** argv) {
        ogg_sync_state the_ogg_sync_state;
        ogg_stream_state the_ogg_stream_state;
        ogg_page the_ogg_page;
        ogg_packet the_ogg_packet;
        char* buffer;
        size_t bytes_actually_read;
        FILE* source;

        if (argc < 2) {
                printf("No file\n");
                return 0;
        }

        source = fopen(argv[1], "r");
        if (feof(source) != 0) {
                printf("Empty file\n");
                fclose(source);
                return 0;
        }

        ogg_sync_init(&the_ogg_sync_state);
        ogg_stream_init(&the_ogg_stream_state, 0);

        do {
                if (ogg_sync_pageout(&the_ogg_sync_state, &the_ogg_page)
== 1) {
                        printf("Decode Page\n");
                        send_to_my_decoder( the_ogg_page.body,
the_ogg_page.body_len );

                        ogg_stream_pagein(&the_ogg_stream_state,
&the_ogg_page);

                        ogg_stream_packetout(&the_ogg_stream_state,
&the_ogg_packet);

                        printf("Decode Packet\n");
                        send_to_my_decoder( the_ogg_packet.packet,
the_ogg_packet.bytes );
                }

                buffer = ogg_sync_buffer(&the_ogg_sync_state, BUF_SIZE);

                bytes_actually_read = fread(buffer, 1, BUF_SIZE, source);

                ogg_sync_wrote(&the_ogg_sync_state, bytes_actually_read);
        } while (feof(source) == 0 );

        ogg_stream_clear( &the_ogg_stream_state );
        ogg_sync_clear( &the_ogg_sync_state );

        fclose(source);

        return 1;
}
>>>
$ ./a.out 320x240.ogg | head -20
Decode Page
Magic!
Decode Packet
not a header
Decode Page
Magic!
Decode Packet
not a header
Decode Page
not a header
Decode Packet
not a header
Decode Page
not a header
Decode Packet
not a header
Decode Page
not a header
Decode Packet
not a header

2008/4/29 Neil Leathers <neil.leathers at
rogers.com>:
>         do {
>                 if (ogg_sync_pageout(&the_ogg_sync_state,
&the_ogg_page) == 1) {
>                         printf("Decode Page\n");
>                         send_to_my_decoder( the_ogg_page.body,
the_ogg_page.body_len );
>
>                         ogg_stream_pagein(&the_ogg_stream_state,
&the_ogg_page);
>
>                         ogg_stream_packetout(&the_ogg_stream_state,
&the_ogg_packet);
>
>                         printf("Decode Packet\n");
>                         send_to_my_decoder( the_ogg_packet.packet,
the_ogg_packet.bytes );
>                 }
you need to loop on the call to ogg_stream_packetout(), because a page
may contain any number (0, 1, 2, ...) of completed packets.

Conrad.

> >         do {
> >                 if (ogg_sync_pageout(&the_ogg_sync_state,
&the_ogg_page) == 1) {
> >                         printf("Decode Page\n");
> >                         send_to_my_decoder( the_ogg_page.body,
the_ogg_page.body_len );
> >
> >                         ogg_stream_pagein(&the_ogg_stream_state,
&the_ogg_page);
> >
> >                        
ogg_stream_packetout(&the_ogg_stream_state, &the_ogg_packet);
> >
> >                         printf("Decode Packet\n");
> >                         send_to_my_decoder( the_ogg_packet.packet,
the_ogg_packet.bytes );
> >                 }
> 
> you need to loop on the call to ogg_stream_packetout(), because a page
> may contain any number (0, 1, 2, ...) of completed packets.
I also lacked the serial numbers on the streams.

if (ogg_sync_pageout(&the_ogg_sync_state, &the_ogg_page) == 1) {
	key = ogg_page_serialno( &the_ogg_page);

	the_ogg_stream_state = get(&hash_table, key);

	if (the_ogg_stream_state == NULL) {
		the_ogg_stream_state = malloc( sizeof(ogg_stream_state) );

		ogg_stream_init(the_ogg_stream_state, key);

		insert(&hash_table, key, the_ogg_stream_state);
	}

	ogg_stream_pagein(the_ogg_stream_state, &the_ogg_page);

	while (ogg_stream_packetout(the_ogg_stream_state, &the_ogg_packet) != 0) {
		send_to_my_decoder( key, the_ogg_packet.packet, the_ogg_packet.bytes );
	}
}

Everything seems to be working now. Thanks,

Neil