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commit 6efd7da028992742c178852dccd99ebf539c414c Author: Lynne <[email protected]> AuthorDate: Sun Sep 20 20:59:47 2026 +0900 Commit: Lynne <[email protected]> CommitDate: Thu Sep 24 08:03:43 2026 +0900 ffv1enc_vulkan: fix the float32 remap coding after a run of consecutive values The encoder kept its own bookkeeping of the last coded value and of a pending run of consecutive values, and ended a run by coding its length followed by a zero-length run. The decoder however skips one value after every run and stays in run mode, so a value exactly two above the last value of a run is coded as the start of the next run, not as a step from the value that was skipped. The encoder coded a wrapped-around step of 0xFFFFFFFF for it instead, which sent the decoder past the end of the value range and corrupted the rest of the slice. Slices with enough distinct values for this to happen only occur from around 3K upwards. Rewrite the coder to walk the decoder's state machine, coding every symbol relative to the decoder's cursor, and only code the multiplier after the first value when the decoder is going to read it. --- libavcodec/vulkan/ffv1_enc_setup.comp.glsl | 118 ++++++++++++++--------------- 1 file changed, 57 insertions(+), 61 deletions(-) diff --git a/libavcodec/vulkan/ffv1_enc_setup.comp.glsl b/libavcodec/vulkan/ffv1_enc_setup.comp.glsl index 8b6b057e1c..0b28dd4003 100644 --- a/libavcodec/vulkan/ffv1_enc_setup.comp.glsl +++ b/libavcodec/vulkan/ffv1_enc_setup.comp.glsl @@ -122,12 +122,34 @@ void encode_histogram_remap(uint slice_idx, inout SliceContext sc) * lu = 0,1 and category = 0 (run/step-1), 1 (delta, unused here), 2 (mul). */ #define CTX_F32(lu, cat) ((uint(lu)*3u + uint(cat))*CONTEXT_SIZE) +void set_compact_index(uint plane_base, uint bitmap_base, uint pixel_num, + inout uint i, int ci) +{ + const uint u_val = fltmap[plane_base + 2u*i + 0u]; + + /* Assign the index to every pixel with this value (sorted, so adjacent) */ + do { + fltmap[bitmap_base + fltmap[plane_base + 2u*i + 1u]] = uint(ci); + i++; + } while (i < pixel_num && fltmap[plane_base + 2u*i + 0u] == u_val); +} + +/* Codes the sorted unique values of each plane by mirroring the decoder's + * state machine. The decoder walks a cursor over the 32-bit value range and + * alternates between two modes: + * lu == 0: reads run, emits the single value (cursor + run), moves the + * cursor past it, and switches to lu == 1 if run was 0. + * lu == 1: reads run, emits run consecutive values starting at the cursor, + * skips one value, and switches to lu == 0 if run was 0. + * It stops once the cursor is past 0xFFFFFFFF. A single multiplier of 1 is + * used (mul_count == 1), so every value is coded with unit steps. */ void encode_float32_remap(uint slice_idx, inout SliceContext sc) { const uint slice_w = uint(sc.slice_dim.x); const uint slice_h = uint(sc.slice_dim.y); const uint pixel_num = slice_w * slice_h; const uint plane_stride = max_pixels_per_slice*3u; + const int64_t end = int64_t(0xFFFFFFFFu); for (int p = 0; p < color_planes; p++) { /* Layout: per (slice, plane) we have units (max_pixels*8 bytes) @@ -139,90 +161,64 @@ void encode_float32_remap(uint slice_idx, inout SliceContext sc) for (int i = 0; i < NB_CONTEXTS*CONTEXT_SIZE; i++) rc_state[i] = uint8_t(128); + /* mul_count */ put_usymbol(1, CTX_F32(0, 0)); for (int i = 0; i < NB_CONTEXTS*CONTEXT_SIZE; i++) rc_state[i] = uint8_t(128); - /* last_val is the last unique value (or 0xFFFFFFFF as the "before - * any value" sentinel, this lets step = val - last_val give val+1 - * for the first emission via unsigned wraparound). */ - uint last_val = 0xFFFFFFFFu; + int64_t cursor = 0; uint lu = 0; - uint run = 0; int ci = -1; - bool emit_first_mul = true; - - for (uint i = 0; i < pixel_num; i++) { - uint u_val = fltmap[plane_base + 2u*i + 0u]; - uint u_ndx = fltmap[plane_base + 2u*i + 1u]; + uint i = 0; - /* Duplicate of the previous unique value? Reuse ci. */ - if (i > 0u && last_val == u_val) { - fltmap[bitmap_base + u_ndx] = uint(ci); + while (cursor <= end) { + if (i >= pixel_num) { + /* No values left: move the decoder's cursor past the end */ + if (lu == 0u) { + put_usymbol(uint(end + 1 - cursor), CTX_F32(0, 0)); + cursor = end + 1; + } else { + put_usymbol(0, CTX_F32(1, 0)); + cursor++; + lu = 0; + } continue; } - uint step = u_val - last_val; - if (lu == 0u) { - put_usymbol(step - 1u, CTX_F32(0, 0)); + const int64_t val = int64_t(fltmap[plane_base + 2u*i + 0u]); + const uint run = uint(val - cursor); - if (emit_first_mul) { + put_usymbol(run, CTX_F32(0, 0)); + + /* The decoder reads the multiplier right after the first + * value, unless that value is the last possible one */ + if (ci < 0 && val < end) put_usymbol(1, CTX_F32(0, 2)); - emit_first_mul = false; - } - last_val = u_val; - if (step == 1u) { - lu = 1; - run = 0; - } - } else { - if (step == 1u) { - run++; - last_val = u_val; - } else { - if (run > 0u) { - put_usymbol(run, CTX_F32(1, 0)); - put_usymbol(0, CTX_F32(1, 0)); - last_val += 2u; - } else { - put_usymbol(0, CTX_F32(1, 0)); - last_val += 1u; - } - lu = 0; - run = 0; + set_compact_index(plane_base, bitmap_base, pixel_num, i, ++ci); - step = u_val - last_val; - put_usymbol(step - 1u, CTX_F32(0, 0)); + cursor = val + 1; + lu = uint(run == 0u); + } else { + uint run = 0; - last_val = u_val; - if (step == 1u) { - lu = 1; - run = 0; - } + while (i < pixel_num && + int64_t(fltmap[plane_base + 2u*i + 0u]) == cursor) { + set_compact_index(plane_base, bitmap_base, pixel_num, i, ++ci); + cursor++; + run++; } - } - - ci++; - fltmap[bitmap_base + u_ndx] = uint(ci); - } - if (lu == 1u) { - if (run > 0u) { put_usymbol(run, CTX_F32(1, 0)); - put_usymbol(0, CTX_F32(1, 0)); - last_val += 2u; - } else { - put_usymbol(0, CTX_F32(1, 0)); - last_val += 1u; + + /* The decoder skips one value after a run */ + cursor++; + lu = uint(run != 0u); } } - if (last_val != 0xFFFFFFFFu) - put_usymbol(0xFFFFFFFFu - last_val, CTX_F32(0, 0)); - sc.remap_count[p] = ci + 1; } } -- To stop receiving notification emails like this one, please contact [email protected]. _______________________________________________ ffmpeg-cvslog mailing list -- [email protected] To unsubscribe send an email to [email protected]
