[FFmpeg-devel] [PATCH v1 2/3] avcodec/jpeg2000dec: add support for HTJ2K block decoding
Michael Niedermayer
michael at niedermayer.cc
Mon Apr 3 01:17:43 EEST 2023
On Fri, Mar 31, 2023 at 08:29:40AM -0700, pal at sandflow.com wrote:
> From: caleb <etemesicaleb at gmail.com>
[...]
> @@ -1113,8 +1117,29 @@ static int jpeg2000_decode_packet(Jpeg2000DecoderContext *s, Jpeg2000Tile *tile,
> }
> }
>
> - if ((ret = get_bits(s, av_log2(newpasses1) + cblk->lblock)) < 0)
> - return ret;
> + if (newpasses > 1 && s->is_htj2k) {
> + // Retrieve pass lengths for each pass
> + int href_passes = (cblk->npasses + newpasses - 1) % 3;
> + int segment_passes = newpasses - href_passes;
> + int pass_bound = 2;
> + int eb = 0;
> + int extra_bit = newpasses > 2 ? 1 : 0;
> + while (pass_bound <=segment_passes) {
> + eb++;
> + pass_bound +=pass_bound;
> + }
something with av_log2() should be able to do this simpler
[...]
> +/**
> + * Drops bits from lower bits in the bit buffer. buf contains the bit buffers.
> + * nbits is the number of bits to remove.
> + */
> +av_always_inline
> +static void jpeg2000_bitbuf_drop_bits_lsb(StateVars *buf, uint8_t nbits)
> +{
> + if (buf->bits_left < nbits) {
> + av_log(NULL, AV_LOG_ERROR, "Invalid bit read of %d, bits in buffer are %d\n", nbits, buf->bits_left);
> + av_assert0(0);
[...]
> +int
> +ff_jpeg2000_decode_htj2k(const Jpeg2000DecoderContext *s, Jpeg2000CodingStyle *codsty, Jpeg2000T1Context *t1, Jpeg2000Cblk *cblk,
> + int width, int height, int magp, uint8_t roi_shift)
> +{
> + uint8_t p0 = 0; // Number of placeholder passes
> + uint32_t Lcup; // Length of HT cleanup segment
> + uint32_t Lref; // Length of Refinement segment
> + uint32_t Scup; // HT cleanup segment suffix length
> + uint32_t Pcup; // HT cleanup segment prefix length
> +
> + uint8_t S_blk; // Number of skipped magnitude bitplanes
> + uint8_t pLSB;
> +
> + uint8_t *Dcup; // Byte of an HT cleanup segment
> + uint8_t *Dref; // Byte of an HT refinement segment
> +
> + int z_blk; // Number of ht coding pass
> +
> + uint8_t empty_passes;
> +
> + StateVars mag_sgn; // Magnitude and Sign
> + StateVars mel; // Adaptive run-length coding
> + StateVars vlc; // Variable Length coding
> + StateVars sig_prop; // Significance propagation
> +
> + MelDecoderState mel_state;
> +
> + int ret;
> +
> + /* Temporary buffers */
> + int32_t *sample_buf;
> + uint8_t *block_states;
> +
> + int32_t n, val; // Post-processing
> +
> + int32_t M_b = magp;
> + av_assert0(width <= 1024U && height <= 1024U);
> + av_assert0(width * height <= 4096);
> + av_assert0(width * height > 0);
Has this decoder been tested with some fuzzer ?
I see a bunch of asserts in it and i dont immedeatly see what would prevent them from
triggering
thx
[...]
--
Michael GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB
"I am not trying to be anyone's saviour, I'm trying to think about the
future and not be sad" - Elon Musk
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