From 9a494b82d998823d0de68cb6b8db83cc451d1781 Mon Sep 17 00:00:00 2001
From: Paul B Mahol <onemda@gmail.com>
Date: Fri, 30 Sep 2022 18:56:43 +0200
Subject: [PATCH] avcodec/mjpegdec: remove not needed operations on channel
 identifiers

---
 libavcodec/mjpegdec.c | 22 ++++++++--------------
 1 file changed, 8 insertions(+), 14 deletions(-)

diff --git a/libavcodec/mjpegdec.c b/libavcodec/mjpegdec.c
index 559bda5e6f..85d1129f30 100644
--- a/libavcodec/mjpegdec.c
+++ b/libavcodec/mjpegdec.c
@@ -373,10 +373,7 @@ int ff_mjpeg_decode_sof(MJpegDecodeContext *s)
     s->v_max         = 1;
     for (i = 0; i < nb_components; i++) {
         /* component id */
-        int id = get_bits(&s->gb, 8);
-        if (id == 0)
-            return AVERROR_INVALIDDATA;
-        s->component_id[i] = id - 1;
+        s->component_id[i] = get_bits(&s->gb, 8);
         h_count[i]         = get_bits(&s->gb, 4);
         v_count[i]         = get_bits(&s->gb, 4);
         /* compute hmax and vmax (only used in interleaved case) */
@@ -401,10 +398,10 @@ int ff_mjpeg_decode_sof(MJpegDecodeContext *s)
                s->component_id[i], s->quant_index[i]);
     }
     if (   nb_components == 4
-        && s->component_id[0] == 'C' - 1
-        && s->component_id[1] == 'M' - 1
-        && s->component_id[2] == 'Y' - 1
-        && s->component_id[3] == 'K' - 1)
+        && s->component_id[0] == 'C'
+        && s->component_id[1] == 'M'
+        && s->component_id[2] == 'Y'
+        && s->component_id[3] == 'K')
         s->adobe_transform = 0;
 
     if (s->ls && (s->h_max > 1 || s->v_max > 1)) {
@@ -526,7 +523,7 @@ int ff_mjpeg_decode_sof(MJpegDecodeContext *s)
                 s->avctx->pix_fmt = s->bits <= 9 ? AV_PIX_FMT_BGR24 : AV_PIX_FMT_BGR48;
             else {
                 if (   s->adobe_transform == 0
-                    || s->component_id[0] == 'R' - 1 && s->component_id[1] == 'G' - 1 && s->component_id[2] == 'B' - 1) {
+                    || s->component_id[0] == 'R' && s->component_id[1] == 'G' && s->component_id[2] == 'B') {
                     s->avctx->pix_fmt = s->bits <= 8 ? AV_PIX_FMT_GBRP : AV_PIX_FMT_GBRP16;
                 } else {
                     if (s->bits <= 8) s->avctx->pix_fmt = s->cs_itu601 ? AV_PIX_FMT_YUV444P : AV_PIX_FMT_YUVJ444P;
@@ -599,7 +596,7 @@ int ff_mjpeg_decode_sof(MJpegDecodeContext *s)
         case 0x14111100:
         case 0x22211100:
         case 0x22112100:
-            if (s->component_id[0] == 'Q' && s->component_id[1] == 'F' && s->component_id[2] == 'A') {
+            if (s->component_id[0] == 'R' && s->component_id[1] == 'G' && s->component_id[B] == 'B') {
                 if (s->bits <= 8) s->avctx->pix_fmt = AV_PIX_FMT_GBRP;
                 else
                     goto unk_pixfmt;
@@ -614,7 +611,7 @@ int ff_mjpeg_decode_sof(MJpegDecodeContext *s)
             }
             break;
         case 0x21111100:
-            if (s->component_id[0] == 'Q' && s->component_id[1] == 'F' && s->component_id[2] == 'A') {
+            if (s->component_id[0] == 'R' && s->component_id[1] == 'G' && s->component_id[2] == 'B') {
                 if (s->bits <= 8) s->avctx->pix_fmt = AV_PIX_FMT_GBRP;
                 else
                     goto unk_pixfmt;
@@ -1681,9 +1678,6 @@ int ff_mjpeg_decode_sos(MJpegDecodeContext *s, const uint8_t *mb_bitmask,
     }
     for (i = 0; i < nb_components; i++) {
         id = get_bits(&s->gb, 8);
-        if (id == 0)
-            return AVERROR_INVALIDDATA;
-        id -= 1;
         av_log(s->avctx, AV_LOG_DEBUG, "component: %d\n", id);
         /* find component index */
         for (index = 0; index < s->nb_components; index++)