mad-dev December 2005

mad-dev@lists.mars.org

1 participants
4 discussions

repetative decoding of last frame why
by prafulla chandra 24 Dec '05

24 Dec '05

Hi all, finally i am almost succeded in the mp3 decoding with buffering concept except in the decoding of last buffer .for last buffer i am dynamically creating memory and appending MAD_BUFFER_GAURD. what i am getting 2-12 more no. of frames extra compared to the memory mapping approch in the minimad.cwhy is this so ?? can any one tell where the problem is ?? below i am providing our modified input callback function. thanks in advance. prafulla chandra. FILE *fptr; FILE *pfOutput; int function(int length); void moving_fb_decodeengine(int move_length,int destination); static char memory[4096]; static char buffer_frame[4096]; static int instant_memory_size = 4096; static unsigned long framesdecoded; static int remainmemory_length; static unsigned long offset ; static int flag ; static int count; static enum mad_flow input(void *data, struct mad_stream *stream) { struct buffer *buffer = data ; int ltb_shifted,i; unsigned char temp; unsigned char *finalbuffer; int end; int destination; if(!buffer->length) { printf("total number of frames decoded %ld are ",framesdecoded); return MAD_FLOW_STOP; } if(flag==0) { end=function(instant_memory_size); if(!end) { destination=1; } else destination=0; moving_fb_decodeengine(instant_memory_size,destination); } else { ltb_shifted =stream->next_frame-buffer->start; remainmemory_length=instant_memory_size-ltb_shifted; for(i=0;i<instant_memory_size;i++) { if(i==remainmemory_length) { end = function(ltb_shifted); if(!end) { destination=1; } else destination=0; moving_fb_decodeengine(ltb_shifted,destination); break ; } temp=memory[i+ltb_shifted]; memory[i]=temp; } } if(!end) { finalbuffer=malloc(count+MAD_BUFFER_GUARD); if(finalbuffer==0) { return MAD_FLOW_BREAK; } memcpy(finalbuffer,memory,count); memset(finalbuffer+count,0,MAD_BUFFER_GUARD); buffer->start=finalbuffer; buffer->length=count+MAD_BUFFER_GUARD; mad_stream_buffer(stream, buffer->start, buffer->length); } else { buffer->length=instant_memory_size; mad_stream_buffer(stream, buffer->start, buffer->length); } if(!end) { buffer->length=0; } flag =1; return MAD_FLOW_CONTINUE; } void moving_fb_decodeengine( int move_length,int destination) { unsigned char temp; int j,l; if(flag!=0) { for(j =0;j<4096;j++) { temp=buffer_frame[j]; memory[remainmemory_length+j]=temp; if(destination) { if(j==count) count=remainmemory_length+j; } } } else { for(l=0;l<instant_memory_size;l++) { temp=buffer_frame[l]; memory[l]=temp; if(destination) { if(l==count) count=l; } } } } int function(int movement_length) { unsigned int controlvar_length_funct=0,i; int cVar1_funct,count1=0; fptr = fopen("BawreNain_1950-Rajkumari-MereRutheHuyeChanda-KidarSharma_Roshan.mp3","rb"); fseek(fptr,offset,SEEK_SET); for(i=0;i<movement_length;i++) { cVar1_funct=fgetc(fptr); if(cVar1_funct==EOF) { count=count1; fclose(fptr); return(0); } else { count1++; buffer_frame[i]=cVar1_funct; offset++; } } fclose(fptr); return(1); }

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decoding errors
by prafulla chandra 20 Dec '05

20 Dec '05

Hi all , we compiled MAD decoder using the High level api giving some chunks of data every time instead of whole file in the input callback.but while compiling most of the times we are getting errors as decoding error 0x0101 (lost synchronization) at byte offset 522 decoding error 0x0103 (forbidden bitrate value) at byte offset 537 decoding error 0x0103 (forbidden bitrate value) at byte offset 538 decoding error 0x0103 (forbidden bitrate value) at byte offset 539 decoding error 0x0103 (forbidden bitrate value) at byte offset 540 decoding error 0x0103 (forbidden bitrate value) at byte offset 541 . .................... .... ..........this continues and after some time we are getting decoding error 0x0235 (bad main_data_begin pointer) at byte offset 1024 decoding error 0x0101 (lost synchronization) at byte offset 522 decoding error 0x0101 (lost synchronization) at byte offset 897 decoding error 0x0235 (bad main_data_begin pointer) at byte offset 1039 decoding error 0x0101 (lost synchronization) at byte offset 522 decoding error 0x0101 (lost synchronization) at byte offset 699 decoding error 0x0103 (forbidden bitrate value) at byte offset 714 decoding error 0x0103 (forbidden bitrate value) at byte offset 715 decoding error 0x0104 (reserved sample frequency value) at byte offset 716 decoding error 0x0102 (reserved header layer value) at byte offset 874 decoding error 0x0103 (forbidden bitrate value) at byte offset 876 .. ........... ............. why these errors are coming ........will these errors have any impact on the final output pcm file size?? means any data lost?? bcz i am getting 50MB as output pcm file size rather than 55MB(using other softwares like COOL EDIT). can someone points out where the problem is? Please kindly indicates me some clues to fix the problem. Thanks in advance prafulla chandra.

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buffering using the high level api
by prafulla chandra 17 Dec '05

17 Dec '05

Hi all, as I told earlier I am doing mp3 streaming using high level api of MAD decoder for buffering I am using the "*streamnextframe*" which is in the * frame.c* file and for the beginning frame address I am using "*framebegin " *which is in the *stream.c . *By using these two variables I am filling the buffer in the *input callback*.with this concept I am able to decode the song .with some errors messages are comming as bad data pointer ,forbidden bitrate value etc.........and while playing in the winamp some little noise and some of the song words are some what changed(Pronunciation is different but perceptually identifiable )at every 20 sec or 30 sec ( this time duration is varying some times) .whether my concept of filling the buffer with those variables are correct or not .next problem is I am converting the output file into WAV file using the software and at the same time I am giving the same input file to the other soft wares which will convert directly from MP3 to WAV . then what I feel was the file size I am getting is less compared to the other one (software decoded). why is it so .where is the problem . I am some what suspicious above concept. whether that is correct or not .if it is not what i have to do and how I have to make links with the decode engine in such a way that i can able to play the song with buffering concept. thanks in advance regards, prafulla chandra

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how to implement input buffer to execute mad
by prafulla chandra 03 Dec '05

03 Dec '05

Hi all, i am working on mad code to decode the mp3 .my requirement is instead of giving the whole file as input to the mad decoder i have to give the input of 8k every time . what i understand from the code is it will ask for input when ever there is insufficient data to decode the frame that time it will refer input buffer using the input callback. i am extracting frame by frame by using the same sync search algorithm.now these extracted frame i am keeping in the 8k buffer at the initial time .when ever it asks for data i am loading the next frame into the buffer by deleating the first frame in the buffer and moving the remaining data to that possition and appending the new frame at the last . now my doubt is how many frames i have to keep in the input buffer and how i have to link this code in the original mad code means, how my code has to communicate with the mad code ,where i have to do the changes to achieve the same.and in how many approches this can be achieved .because this is my idea only i dont know how to do manupulations and where to do in the code whether my approch is correct or not ,if not please tell how i have to approch for this problem . regards, prafulla chandra.

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mad-dev December 2005