> yes, please resbmit the remaining patch/changes with any comments
> from everyone taken care of or with explanation why not
>
> thx
Here you go, squashed into one patch.
Sentences ending with a period have been capitalized and printf typecasts
removed (Moritz).
Jonathan Campbell
From 8d64027573588a62728faebba55d67c00a3d4e3f Mon Sep 17 00:00:00 2001
From: Jonathan Campbell <jonat...@castus.tv>
Date: Wed, 14 Sep 2016 10:57:04 -0700
Subject: [PATCH] Read cc words field-wise, limit to cc_count and support extra
field.
This code validates the cc words the same as the prior code this
replaced in case cc_count is too large. Field counting is used in case
caption source does not use the LSB to signal even/odd field.
---
libavcodec/mpeg12dec.c | 45 ++++++++++++++++++++++++++++++++-------------
1 file changed, 32 insertions(+), 13 deletions(-)
diff --git a/libavcodec/mpeg12dec.c b/libavcodec/mpeg12dec.c
index ca51c97..7c65f77 100644
--- a/libavcodec/mpeg12dec.c
+++ b/libavcodec/mpeg12dec.c
@@ -2265,6 +2265,7 @@ static int mpeg_decode_a53_cc(AVCodecContext *avctx,
/* extract DVD CC data
*
* uint32_t user_data_start_code 0x000001B2 (big endian)
+ * -------------------- p[0] starts here ---------------------
* uint16_t user_identifier 0x4343 "CC"
* uint8_t user_data_type_code 0x01
* uint8_t caption_block_size 0xF8
@@ -2273,7 +2274,7 @@ static int mpeg_decode_a53_cc(AVCodecContext *avctx,
* bit 6 caption_filler 0
* bit 5:1 caption_block_count number of caption blocks
(pairs of caption words = frames). Most DVDs use 15 per start of GOP.
* bit 0 caption_extra_field_added 1=one additional caption word
- *
+ * -------------------- p[5] starts here ---------------------
* struct caption_field_block {
* uint8_t
* bit 7:1 caption_filler 0x7F (all 1s)
@@ -2287,30 +2288,48 @@ static int mpeg_decode_a53_cc(AVCodecContext *avctx,
* Don't assume that the first caption word is the odd field. There do
exist MPEG files in the wild that start
* on the even field. There also exist DVDs in the wild that encode an
odd field count and the
* caption_extra_field_added/caption_odd_field_first bits change per
packet to allow that. */
- int cc_count = 0;
+ int caption_block_count = p[4] & 0x3F; /* you can treat bits 5:0 as
number of fields */
+ int cc_count = 0; /* number of caption fields */
int i;
- // There is a caption count field in the data, but it is often
- // incorrect. So count the number of captions present.
- for (i = 5; i + 6 <= buf_size && ((p[i] & 0xfe) == 0xfe); i += 6)
+
+ for (i = 5; cc_count < caption_block_count && (i + 3) <= buf_size; i
+= 3) {
+ if ((p[i] & 0xfe) != 0xfe) {
+ av_log(avctx, AV_LOG_DEBUG, "cc_count is too large (%d > %d)
or junk data in DVD caption packet\n",caption_block_count,cc_count);
+ break;
+ }
+
cc_count++;
+ }
+
// Transform the DVD format into A53 Part 4 format
if (cc_count > 0) {
av_freep(&s1->a53_caption);
- s1->a53_caption_size = cc_count * 6;
+ s1->a53_caption_size = cc_count * 3;
s1->a53_caption = av_malloc(s1->a53_caption_size);
if (s1->a53_caption) {
- uint8_t field1 = !!(p[4] & 0x80);
+ uint8_t field1 = (p[4] >> 7) & 1; /* caption_odd_field_first */
+ uint8_t pfield = 0xFF; /* DVDs that don't use the
caption_field_odd bit always seem to leave it on */
uint8_t *cap = s1->a53_caption;
+
p += 5;
for (i = 0; i < cc_count; i++) {
- cap[0] = (p[0] == 0xff && field1) ? 0xfc : 0xfd;
+ /* If the source actually uses the caption_odd_field bit,
then use that to determine the field.
+ * Else, toggle between fields to keep track for DVDs
where p[0] == 0xFF at all times. */
+ if (p[0] != pfield)
+ field1 = p[0] & 1; /* caption_field_odd */
+
+ /* in A53 part 4, 0xFC = odd field, 0xFD = even field */
+ cap[0] = field1 ? 0xFC : 0xFD;
cap[1] = p[1];
cap[2] = p[2];
- cap[3] = (p[3] == 0xff && !field1) ? 0xfc : 0xfd;
- cap[4] = p[4];
- cap[5] = p[5];
- cap += 6;
- p += 6;
+
+ av_log(avctx, AV_LOG_DEBUG, "DVD CC field1=%u(%s)
0x%02x%02x prev=0x%02x cur=0x%02x\n",
+ field1,field1?"odd":"even",cap[1],cap[2],pfield,p[0]);
+
+ pfield = p[0];
+ field1 ^= 1;
+ cap += 3;
+ p += 3;
}
}
}
--
2.2.2
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