[FFmpeg-soc] BFI Decoder

[Michael Niedermayer]

On Thu, Apr 17, 2008 at 02:20:08PM +0530, Sisir Koppaka wrote:
> Updated decoder attached.
> -----------------
> Sisir Koppaka

[...]

> static int bfi_decode_init(AVCodecContext * avctx)
> {
>     BFIContext *bfi = avctx->priv_data;
>     bfi->frame.reference = 1;

>     bfi->frame.buffer_hints =
>         FF_BUFFER_HINTS_VALID | FF_BUFFER_HINTS_READABLE |
>         FF_BUFFER_HINTS_PRESERVE | FF_BUFFER_HINTS_REUSABLE;

As you copy the data from an internal buffer to AVFrame these make no
sense.

[...]
> static int bfi_decode_frame(AVCodecContext * avctx, void *data,
>                             int *data_size, const uint8_t * buf,
>                             int buf_size)
> {
>     BFIContext *bfi = avctx->priv_data;
>     uint8_t *dst;
>     uint8_t *src;
>     uint8_t *dst_offset;
>     uint8_t colour1, colour2;
>     uint32_t *pal;
>     uint8_t *frame_end;
>     unsigned int code, byte, length, offset, height = avctx->height;
>     int remaining = avctx->width, i, j;

>     const int wrap_to_next_line = bfi->frame.linesize[0];

redundant


>     if (avctx->reget_buffer(avctx, &bfi->frame)) {
>         av_log(avctx, AV_LOG_ERROR, "reget_buffer() failed\n");
>         return -1;
>     }
>     //avcodec_set_dimensions(avctx, avctx->width, avctx->height); //Check this.
>     dst = bfi->dst;
>     frame_end = bfi->dst + avctx->width * avctx->height;
>     if(bfi->toggle) {
>         bfi->frame.pict_type = FF_I_TYPE;
>         bfi->frame.key_frame = 1;

>         /* Converts the given 6-bit palette values(0-63) to 8-bit values(0-255) */
>         for (i = 0; i < avctx->extradata_size; i++)
>             avctx->extradata[i] =
>                 (avctx->extradata[i] << 2) | (avctx->extradata[i] >> 4);

A decoder cannot write in extradata


>         /* Setting the palette */
>         pal = (uint32_t *) bfi->frame.data[1]; 
>         for (i = 0; i < 256; i++)
>             *pal++ = AV_RB24(&avctx->extradata[i*3]);
>         bfi->frame.palette_has_changed = 1;
>         av_log(NULL,AV_LOG_INFO, "\n[DECODER] Palette has been set.");  
>         bfi->toggle = 0;
>     }
>     else
>     {
>         bfi->frame.pict_type = FF_P_TYPE;
>         bfi->frame.key_frame = 0;
>     }
>         

trailing whitespace


>     while (dst != frame_end) {
>         byte = *buf++;
>         code = byte >> 6;
>         length = byte & ~0xC0;
>         if (length == 0) {
>            if(code == 1) {
>                length = bytestream_get_byte(&buf);
>                offset = bytestream_get_le16(&buf);
>            }
>            else {
>               length = bytestream_get_le16(&buf);
>               if(code == 2)
>                   goto finish;
>            }               
>         }
>         else {
>             if(code == 1)
>                 offset = bytestream_get_byte(&buf);
>         }

inconsistant indention


>         switch (code) {
>         case 0:                //Normal Chain
>             if(dst+length>frame_end)
>                 break;
>             bytestream_get_buffer(&buf, dst, length);
>             dst += length;
>             av_log(NULL,AV_LOG_INFO, "\n[DECODER] Normal Chain.");
>             break;
>         case 1:                //Back Chain
>             dst_offset = dst - offset;
>             length *= 4;        //Convert dwords to bytes.
>             if(dst+length>frame_end || dst_offset<bfi->dst)
>                 break;

>             while(length--)
>             {
>                 *dst++ = *dst_offset++;
>             }

superflous {}


>             av_log(NULL,AV_LOG_INFO, "\n[DECODER] Back Chain.");
>             break;
>         case 2:                //Skip Chain

>             if(dst+length>frame_end)
>                 break;

duplicate


>             dst += length;
>             av_log(NULL,AV_LOG_INFO, "\n[DECODER] Skip Chain.");                                  
>             break;
>         case 3:                //Fill Chain
>             colour1 = bytestream_get_byte(&buf);
>             colour2 = bytestream_get_byte(&buf);
>             if(dst+length*2>frame_end)
>                 break;
>             while(length--)
>             {
>                 *dst++ = colour1;
>                 *dst++ = colour2;
>             }
>             av_log(NULL,AV_LOG_INFO, "\n[DECODER] Fill Chain.");
>             break;

>         default:
>             av_log(NULL, AV_LOG_INFO,
>                    "\nOops! Couldn't recognize the 'code'...");

in which case can this be reached?


[...]

-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

I have never wished to cater to the crowd; for what I know they do not
approve, and what they approve I do not know. -- Epicurus
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