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commit 5672c410a6adc2764791e7fcc0e34acea07ac263 Author: Ramiro Polla <[email protected]> AuthorDate: Wed Oct 8 19:48:49 2025 +0200 Commit: Ramiro Polla <[email protected]> CommitDate: Fri Feb 20 16:32:10 2026 +0100 avcodec/mjpegdec: unescape data for each restart marker individually Instead of unescaping the entire image data buffer in advance, and then having to perform heuristics to skip over where the restart markers would have been, unescape the image data for each restart marker individually. --- libavcodec/mjpegbdec.c | 1 - libavcodec/mjpegdec.c | 130 +++++++++++++++++++------------------------------ libavcodec/mjpegdec.h | 30 ++++++++++++ 3 files changed, 81 insertions(+), 80 deletions(-) diff --git a/libavcodec/mjpegbdec.c b/libavcodec/mjpegbdec.c index 2c1747f502..e627ab810a 100644 --- a/libavcodec/mjpegbdec.c +++ b/libavcodec/mjpegbdec.c @@ -61,7 +61,6 @@ static int mjpegb_decode_frame(AVCodecContext *avctx, AVFrame *rframe, read_header: /* reset on every SOI */ s->restart_interval = 0; - s->restart_count = 0; s->mjpb_skiptosod = 0; if ((ret = init_get_bits8(&hgb, buf_ptr, /*buf_size*/(buf_end - buf_ptr))) < 0) diff --git a/libavcodec/mjpegdec.c b/libavcodec/mjpegdec.c index 1cbeecd01c..2499bade57 100644 --- a/libavcodec/mjpegdec.c +++ b/libavcodec/mjpegdec.c @@ -57,7 +57,6 @@ static void mjpeg_find_raw_scan_data(MJpegDecodeContext *s, const uint8_t **pbuf_ptr, size_t *pbuf_size); -static int mjpeg_unescape_sos(MJpegDecodeContext *s); static int init_default_huffman_tables(MJpegDecodeContext *s) { @@ -1076,40 +1075,6 @@ static int decode_block_refinement(MJpegDecodeContext *s, int16_t *block, #undef REFINE_BIT #undef ZERO_RUN -static int handle_rstn(MJpegDecodeContext *s, int nb_components) -{ - int i; - int reset = 0; - - if (s->restart_interval) { - s->restart_count--; - if(s->restart_count == 0 && s->avctx->codec_id == AV_CODEC_ID_THP){ - align_get_bits(&s->gb); - for (i = 0; i < nb_components; i++) /* reset dc */ - s->last_dc[i] = (4 << s->bits); - } - - i = 8 + ((-get_bits_count(&s->gb)) & 7); - /* skip RSTn */ - if (s->restart_count == 0) { - if( show_bits(&s->gb, i) == (1 << i) - 1 - || show_bits(&s->gb, i) == 0xFF) { - int pos = get_bits_count(&s->gb); - align_get_bits(&s->gb); - while (get_bits_left(&s->gb) >= 8 && show_bits(&s->gb, 8) == 0xFF) - skip_bits(&s->gb, 8); - if (get_bits_left(&s->gb) >= 8 && (get_bits(&s->gb, 8) & 0xF8) == 0xD0) { - for (i = 0; i < nb_components; i++) /* reset dc */ - s->last_dc[i] = (4 << s->bits); - reset = 1; - } else - skip_bits_long(&s->gb, pos - get_bits_count(&s->gb)); - } - } - } - return reset; -} - /* Handles 1 to 4 components */ static int ljpeg_decode_rgb_scan(MJpegDecodeContext *s) { @@ -1141,8 +1106,6 @@ static int ljpeg_decode_rgb_scan(MJpegDecodeContext *s) } - s->restart_count = s->restart_interval; - for (i = 0; i < 6; i++) vpred[i] = 1 << (s->bits-1); @@ -1160,6 +1123,8 @@ static int ljpeg_decode_rgb_scan(MJpegDecodeContext *s) for (i = 0; i < 4; i++) buffer[0][i] = 1 << (s->bits - 1); + s->restart_count = -1; + for (mb_y = 0; mb_y < s->mb_height; mb_y++) { uint8_t *ptr = s->picture_ptr->data[0] + (linesize * mb_y); @@ -1171,9 +1136,12 @@ static int ljpeg_decode_rgb_scan(MJpegDecodeContext *s) for (mb_x = 0; mb_x < width; mb_x++) { int modified_predictor = predictor; + int restart; - if (s->restart_interval && !s->restart_count){ - s->restart_count = s->restart_interval; + ret = ff_mjpeg_handle_restart(s, &restart); + if (ret < 0) + return ret; + if (restart) { resync_mb_x = mb_x; resync_mb_y = mb_y; for(i=0; i<4; i++) @@ -1210,11 +1178,6 @@ static int ljpeg_decode_rgb_scan(MJpegDecodeContext *s) left[i] = buffer[mb_x][i] = mask & (pred + (unsigned)(dc * (1 << point_transform))); } - - if (s->restart_interval && !--s->restart_count) { - align_get_bits(&s->gb); - skip_bits(&s->gb, 16); /* skip RSTn */ - } } if (s->rct && s->nb_components == 4) { for (mb_x = 0; mb_x < s->mb_width; mb_x++) { @@ -1299,10 +1262,15 @@ static int ljpeg_decode_yuv_scan(MJpegDecodeContext *s) av_assert0(nb_components>=1 && nb_components<=4); + s->restart_count = -1; + for (mb_y = 0; mb_y < s->mb_height; mb_y++) { for (mb_x = 0; mb_x < s->mb_width; mb_x++) { - if (s->restart_interval && !s->restart_count){ - s->restart_count = s->restart_interval; + int restart; + ret = ff_mjpeg_handle_restart(s, &restart); + if (ret < 0) + return ret; + if (restart) { resync_mb_x = mb_x; resync_mb_y = mb_y; } @@ -1434,10 +1402,6 @@ static int ljpeg_decode_yuv_scan(MJpegDecodeContext *s) } } } - if (s->restart_interval && !--s->restart_count) { - align_get_bits(&s->gb); - skip_bits(&s->gb, 16); /* skip RSTn */ - } } } return 0; @@ -1487,6 +1451,7 @@ static int mjpeg_decode_scan(MJpegDecodeContext *s) int linesize[MAX_COMPONENTS]; GetBitContext mb_bitmask_gb = {0}; // initialize to silence gcc warning int bytes_per_pixel = 1 + (s->bits > 8); + int ret; if (s->avctx->codec_id == AV_CODEC_ID_MXPEG) { mb_bitmask = s->mb_bitmask; @@ -1501,8 +1466,6 @@ static int mjpeg_decode_scan(MJpegDecodeContext *s) init_get_bits(&mb_bitmask_gb, mb_bitmask, s->mb_width * s->mb_height); } - s->restart_count = 0; - av_pix_fmt_get_chroma_sub_sample(s->avctx->pix_fmt, &chroma_h_shift, &chroma_v_shift); chroma_width = AV_CEIL_RSHIFT(s->width, chroma_h_shift); @@ -1517,15 +1480,31 @@ static int mjpeg_decode_scan(MJpegDecodeContext *s) } next_field: - for (i = 0; i < nb_components; i++) - s->last_dc[i] = (4 << s->bits); + s->restart_count = -1; for (mb_y = 0; mb_y < s->mb_height; mb_y++) { for (mb_x = 0; mb_x < s->mb_width; mb_x++) { const int copy_mb = mb_bitmask && !get_bits1(&mb_bitmask_gb); + int restart; - if (s->restart_interval && !s->restart_count) - s->restart_count = s->restart_interval; + if (s->avctx->codec_id == AV_CODEC_ID_THP) { + if (s->restart_count < 0) { + ret = ff_mjpeg_unescape_sos(s); + if (ret < 0) + return ret; + } + restart = ff_mjpeg_should_restart(s); + if (restart) + align_get_bits(&s->gb); + } else { + ret = ff_mjpeg_handle_restart(s, &restart); + if (ret < 0) + return ret; + } + if (restart) { + for (i = 0; i < nb_components; i++) + s->last_dc[i] = (4 << s->bits); + } if (get_bits_left(&s->gb) < 0) { av_log(s->avctx, AV_LOG_ERROR, "overread %d\n", @@ -1599,24 +1578,18 @@ next_field: } } } - - handle_rstn(s, nb_components); } } if (s->interlaced && - get_bits_left(&s->gb) > 32 && - show_bits(&s->gb, 8) == 0xFF) { - GetBitContext bak = s->gb; - align_get_bits(&bak); - if (show_bits(&bak, 16) == 0xFFD1) { + bytestream2_get_bytes_left(&s->gB) > 2 && + bytestream2_tell(&s->gB) > 2 && + s->gB.buffer[-2] == 0xFF && + s->gB.buffer[-1] == 0xD1) { av_log(s->avctx, AV_LOG_DEBUG, "AVRn interlaced picture marker found\n"); - s->gb = bak; - skip_bits(&s->gb, 16); s->bottom_field ^= 1; goto next_field; - } } return 0; @@ -1643,7 +1616,7 @@ static int mjpeg_decode_scan_progressive_ac(MJpegDecodeContext *s) // Ss and Se are parameters telling start and end coefficients s->coefs_finished[c] |= (2ULL << Se) - (1ULL << Ss); - s->restart_count = 0; + s->restart_count = -1; for (mb_y = 0; mb_y < s->mb_height; mb_y++) { int block_idx = mb_y * s->block_stride[c]; @@ -1651,8 +1624,12 @@ static int mjpeg_decode_scan_progressive_ac(MJpegDecodeContext *s) uint8_t *last_nnz = &s->last_nnz[c][block_idx]; for (mb_x = 0; mb_x < s->mb_width; mb_x++, block++, last_nnz++) { int ret; - if (s->restart_interval && !s->restart_count) - s->restart_count = s->restart_interval; + int restart; + ret = ff_mjpeg_handle_restart(s, &restart); + if (ret < 0) + return ret; + if (restart) + EOBRUN = 0; if (Ah) ret = decode_block_refinement(s, *block, last_nnz, s->ac_index[0], @@ -1668,9 +1645,6 @@ static int mjpeg_decode_scan_progressive_ac(MJpegDecodeContext *s) "error y=%d x=%d\n", mb_y, mb_x); return AVERROR_INVALIDDATA; } - - if (handle_rstn(s, 0)) - EOBRUN = 0; } } return 0; @@ -1816,12 +1790,12 @@ int ff_mjpeg_decode_sos(MJpegDecodeContext *s) return ret; } else { - ret = mjpeg_unescape_sos(s); - if (ret < 0) - return ret; if (s->lossless) { av_assert0(s->picture_ptr == s->picture); if (CONFIG_JPEGLS_DECODER && s->ls) { + ret = ff_mjpeg_unescape_sos(s); + if (ret < 0) + return ret; if ((ret = ff_jpegls_decode_picture(s)) < 0) return ret; } else { @@ -1864,7 +1838,6 @@ static int mjpeg_decode_dri(MJpegDecodeContext *s) if (bytestream2_get_be16u(&s->gB) != 4) return AVERROR_INVALIDDATA; s->restart_interval = bytestream2_get_be16u(&s->gB); - s->restart_count = 0; av_log(s->avctx, AV_LOG_DEBUG, "restart interval: %d\n", s->restart_interval); @@ -2271,7 +2244,7 @@ found_hw: bytestream2_skipu(&s->gB, *pbuf_size); } -static int mjpeg_unescape_sos(MJpegDecodeContext *s) +int ff_mjpeg_unescape_sos(MJpegDecodeContext *s) { const uint8_t *buf_ptr = s->gB.buffer; const uint8_t *buf_end = buf_ptr + bytestream2_get_bytes_left(&s->gB); @@ -2320,7 +2293,7 @@ static int mjpeg_unescape_sos(MJpegDecodeContext *s) bytestream2_put_byteu(&pb, 0xff); } else if (x >= RST0 && x <= RST7) { /* Restart marker */ - bytestream2_put_be16u(&pb, 0xff00 | x); + goto found; } else { /* Non-restart marker */ ptr -= 2; @@ -2502,7 +2475,6 @@ redo_for_pal8: switch (start_code) { case SOI: s->restart_interval = 0; - s->restart_count = 0; s->raw_image_buffer = buf_ptr; s->raw_image_buffer_size = buf_end - buf_ptr; /* nothing to do on SOI */ diff --git a/libavcodec/mjpegdec.h b/libavcodec/mjpegdec.h index 04488c1d2d..29fe5db03e 100644 --- a/libavcodec/mjpegdec.h +++ b/libavcodec/mjpegdec.h @@ -191,5 +191,35 @@ int ff_mjpeg_decode_dht(MJpegDecodeContext *s); int ff_mjpeg_decode_sof(MJpegDecodeContext *s); int ff_mjpeg_decode_sos(MJpegDecodeContext *s); int ff_mjpeg_find_marker(const uint8_t **buf_ptr, const uint8_t *buf_end); +int ff_mjpeg_unescape_sos(MJpegDecodeContext *s); + +static inline int ff_mjpeg_should_restart(MJpegDecodeContext *s) +{ + int restart = 0; + if (s->restart_interval) { + if (s->restart_count <= 0) { + s->restart_count = s->restart_interval; + restart = 1; + } + s->restart_count--; + } else { + if (s->restart_count < 0) { + s->restart_count = 0; + restart = 1; + } + } + return restart; +} + +static inline int ff_mjpeg_handle_restart(MJpegDecodeContext *s, int *restart) +{ + *restart = ff_mjpeg_should_restart(s); + if (*restart) { + int ret = ff_mjpeg_unescape_sos(s); + if (ret < 0) + return ret; + } + return 0; +} #endif /* AVCODEC_MJPEGDEC_H */ _______________________________________________ ffmpeg-cvslog mailing list -- [email protected] To unsubscribe send an email to [email protected]
