[FFmpeg-soc] Bitstream writer from vorbis_enc.c

[Michael Niedermayer]

On Sun, Aug 24, 2008 at 01:56:10AM +0200, Bartlomiej Wolowiec wrote:
> Saturday 23 August 2008 03:33:27 Michael Niedermayer napisał(a):
> > On Sat, Aug 23, 2008 at 12:31:48AM +0200, Bartlomiej Wolowiec wrote:
> > > In nellymoserenc.c is a duplicate of bitstream writer code from
> > > vorbis_enc.c. How should I remove this duplicate? Add to bitstream.h this
> > > code and make activation by BITSTREAM_WRITER_LE available?
> >
> > The put_bits code in vorbis_enc.c is extreemly poorly written and it
> > needs be cleaned up before it can be used by another encoder.
> > Actually i wonder how this code managed to get into svn ...
> >
> > [...]
> 
> I tried to wrote patch to bitstream.h. I hope that it's better than previous 
> code.
> 
> -- 
> Bartlomiej Wolowiec

> Index: bitstream.h
> ===================================================================
> --- bitstream.h	(wersja 14909)
> +++ bitstream.h	(kopia robocza)
> @@ -123,6 +123,7 @@
>  #ifdef ALT_BITSTREAM_WRITER
>      align_put_bits(s);
>  #else
> +#ifndef BITSTREAM_WRITER_LE
>      s->bit_buf<<= s->bit_left;
>      while (s->bit_left < 32) {
>          /* XXX: should test end of buffer */
> @@ -130,6 +131,14 @@
>          s->bit_buf<<=8;
>          s->bit_left+=8;
>      }
> +#else
> +    while (s->bit_left < 32) {
> +        /* XXX: should test end of buffer */
> +        *s->buf_ptr++=s->bit_buf;
> +        s->bit_buf>>=8;
> +        s->bit_left+=8;
> +    }
> +#endif

theres some common code between if and else


>      s->bit_left=32;
>      s->bit_buf=0;
>  #endif
> @@ -190,6 +199,7 @@
>  
>      //    printf("n=%d value=%x cnt=%d buf=%x\n", n, value, bit_cnt, bit_buf);
>      /* XXX: optimize */
> +#ifndef BITSTREAM_WRITER_LE
>      if (n < bit_left) {
>          bit_buf = (bit_buf<<n) | value;
>          bit_left-=n;
> @@ -210,7 +220,27 @@
>          bit_left+=32 - n;
>          bit_buf = value;
>      }
> +#else // BITSTREAM_WRITER_LE
> +    bit_buf |= value << (32 - bit_left);
> +    if (n >= bit_left) {
> +#ifdef UNALIGNED_STORES_ARE_BAD
> +        if (3 & (intptr_t) s->buf_ptr) {
> +            s->buf_ptr[0] = bit_buf;
> +            s->buf_ptr[1] = bit_buf >> 8;
> +            s->buf_ptr[2] = bit_buf >> 16;
> +            s->buf_ptr[3] = bit_buf >> 24;
> +        } else
> +#endif
> +        *(uint32_t *)s->buf_ptr = le2me_32(bit_buf);
> +        s->buf_ptr+=4;
>  

> +        //FIXME: value>>32 == value... ?!

value>>32 == undefined

[...]

-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

The educated differ from the uneducated as much as the living from the
dead. -- Aristotle 
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