[FFmpeg-soc] BFI Decoder

[Sisir Koppaka]

On Thu, Apr 17, 2008 at 3:45 AM, Sisir Koppaka <sisir.koppaka at gmail.com>
wrote:

> 1 : back chain
>       if length is zero, read one more byte of the length AND two bytes of the offset
>        else, read one byte of the offset
>       copy (length) dwords from (output - offset) to the output
>
>       (note, that data may overlap, so don't use memmove() function here, just bare by-dword copying!)
>
>  case 1:                //Back Chain
>             if (length == 0) {
>                 length = bytestream_get_byte(&buf);
>                 offset = bytestream_get_le16(&buf);
>             } else {
>                 offset = bytestream_get_byte(&buf);
>             }
>             dst_offset = dst - offset;
>             length *= 4;        //Convert dwords to bytes.
>             while(length--)
>             {
>                 *dst++ = *dst_offset++;
>             }
>             av_log(NULL,AV_LOG_INFO, "\n[DECODER] Back Chain.");
>             break;
>
> Logically, it doesn't seem to be wrong to me....is it wrong?
>
> I did ./ffmpeg -i file.bfi images/%04d.png but still I only get a blue
> frame, I think the first frame is not decoding...it still segfaults while
> doing decoding a back chain from the av_logs...
>
This might be close to stupid or actually stupid, but I tried changing the
bytestream_get_le16 to be16 just in case, but that didn't work and gave the
same old blue.png....
In a further act of desperation I tried writing dst_offset = dst + offset;
because I'm not sure how the computer is actually addressing the memory
(does next byte necessarily have an incremented address?)(my courses haven't
got that far, if in case this is a well-known fact) this didn't work too...
-----------------
Sisir Koppaka