Comments on alternate approaches are welcome.
From 617cf7adc51f7344fba972fbce42daeab37586e2 Mon Sep 17 00:00:00 2001
From: Alex Converse <[email protected]>
Date: Tue, 17 Nov 2009 12:55:36 -0500
Subject: [PATCH 2/5] Read SBR bits from a second GetBitContext to prevent unrecoverable over-reads
and get automatic under-read protection.
MIME-Version: 1.0
Content-Type: multipart/mixed; boundary="------------1"
This is a multi-part message in MIME format.
--------------1
Content-Type: text/plain; charset=UTF-8; format=fixed
Content-Transfer-Encoding: 8bit
---
aacsbr.c | 14 ++++++++++----
1 files changed, 10 insertions(+), 4 deletions(-)
--------------1
Content-Type: text/x-patch; name="0002-Read-SBR-bits-from-a-second-GetBitContext-to-prevent.patch"
Content-Transfer-Encoding: 8bit
Content-Disposition: attachment; filename="0002-Read-SBR-bits-from-a-second-GetBitContext-to-prevent.patch"
diff --git a/aacsbr.c b/aacsbr.c
index 580dfb1..c652fd5 100644
--- a/aacsbr.c
+++ b/aacsbr.c
@@ -792,9 +792,13 @@ static void sbr_reset(AACContext *ac, SpectralBandReplication *sbr)
* @return Returns number of bytes consumed from the TYPE_FIL element.
*/
int ff_decode_sbr_extension(AACContext *ac, SpectralBandReplication *sbr,
- GetBitContext *gb, int crc, int cnt, int id_aac)
+ GetBitContext *gb_host, int crc, int cnt, int id_aac)
{
unsigned int num_sbr_bits = 0, num_align_bits;
+ unsigned bytes_read;
+ GetBitContext gbc = *gb_host;
+ GetBitContext *gb = &gbc;
+ skip_bits_long(gb_host, cnt*8 - 4);
if (crc) {
skip_bits(gb, 10); // bs_sbr_crc_bits; FIXME - implement CRC check
@@ -812,9 +816,11 @@ int ff_decode_sbr_extension(AACContext *ac, SpectralBandReplication *sbr,
num_sbr_bits += sbr_data(ac, sbr, gb, id_aac);
num_align_bits = ((cnt << 3) - 4 - num_sbr_bits) & 7;
- skip_bits(gb, num_align_bits); // bs_fill_bits
-
- return (num_sbr_bits + num_align_bits + 4) >> 3;
+ bytes_read = ((num_sbr_bits + num_align_bits + 4) / 8);
+ if (bytes_read > cnt) {
+ av_log(ac->avccontext, AV_LOG_ERROR, "Expected to read %d SBR bytes actually read %d.\n", cnt, bytes_read);
+ }
+ return cnt;
}
// Time/frequency Grid (14496-3 sp04 p200)
--------------1--
_______________________________________________
FFmpeg-soc mailing list
[email protected]
https://lists.mplayerhq.hu/mailman/listinfo/ffmpeg-soc
