[FFmpeg-devel] [PATCH 06/10] avcodec/dca_parser: improve frame end search

[foo86]

On Fri, May 20, 2016 at 08:51:53PM -0300, James Almer wrote:
> "ffmpeg -i q4G.dts -c:a copy -f framecrc -" gave me the following
> before the patch
> 
> #software: Lavf57.36.100
> #tb 0: 1/90000
> #media_type 0: audio
> #codec_id 0: dts
> #sample_rate 0: 192000
> #channel_layout 0: 60f
> 0,          0,          0,      960,    15520, 0x4e922c28
> 0,        960,        960,      960,    15620, 0x0aa208ee
> 0,       1920,       1920,      960,    15604, 0x5ff63a0b
> 0,       2880,       2880,      960,    15516, 0xeeabf0c9
> 0,       3840,       3840,      960,    15476, 0x53f46290
> 0,       4800,       4800,      960,    15348, 0x477e8987
> 0,       5760,       5760,      960,    15252, 0x2b20725b
> 0,       6720,       6720,      960,    15304, 0x9d60b356
> 0,       7680,       7680,      960,    15172, 0x19e359e4
> 0,       8640,       8640,      960,    15092, 0x1dc6f776
> 0,       9600,       9600,      960,    15064, 0xc2385e65
> 0,      10560,      10560,      960,    15048, 0x50d75a33
> 0,      11520,      11520,      960,    15132, 0x3eb47e67
> 0,      12480,      12480,      960,    15188, 0x6f16aad6
> 0,      13440,      13440,      960,    15360, 0xc481d7c6
> 0,      14400,      14400,      960,    15508, 0x2da8a9f4
> 0,      15360,      15360,      960,    15380, 0x036fe8c8
> 0,      16320,      16320,      960,    15372, 0xa815aa65
> 0,      17280,      17280,      960,    15352, 0xc9f7b3db
> 0,      18240,      18240,      960,    15288, 0x62a15e11
> 0,      19200,      19200,      960,    12746, 0x44ee1fa5
> 0,      20160,      20160,     1920,     2530, 0xf4a2af4c

Yeah, this may look like combined frame due to doubled duration, but in
fact this 2530 byte frame is a fragment that belongs to the previous
frame (you can tell that the previous frame is shorter by approximately
the same number of bytes). Doubled duration actually comes from
misinterpreted core frame header (parser interprets arbitrary EXSS data
as core frame header).

> 0,      22080,      22080,      960,    15244, 0xa8948fa5
> 0,      23040,      23040,      960,    15264, 0x47539652
> 0,      24000,      24000,      960,    15300, 0x10adf509
> 0,      24960,      24960,      960,    15356, 0x3403a586
> 0,      25920,      25920,      960,    15436, 0xcbea18b7
> 0,      26880,      26880,      960,    15424, 0x2ce91378
> 0,      27840,      27840,      960,    15524, 0xf3ba523c
> 0,      28800,      28800,      960,    15544, 0xa1504354
> 0,      29760,      29760,      960,    15528, 0x6bc826fd
> 0,      30720,      30720,      960,    15492, 0x4f89f07a
> 0,      31680,      31680,      960,    15456, 0x002c4ac0
> 0,      32640,      32640,      960,    15388, 0x78c854be
> 0,      33600,      33600,      960,    15372, 0xce9954e5
> 0,      34560,      34560,      960,    15268, 0x1c5bceda
> 0,      35520,      35520,      960,    15288, 0x60acfb3d
> 0,      36480,      36480,      960,    15240, 0xb42d7f7b
> 0,      37440,      37440,      960,    15316, 0xd6080d5a
> 0,      38400,      38400,      960,    15368, 0xc2b65528
> 0,      39360,      39360,      960,    15476, 0xa01f2806
> 0,      40320,      40320,      960,    15448, 0x2e0121ef
> 0,      41280,      41280,      960,    15384, 0x891dd887
> 0,      42240,      42240,      960,    15384, 0x31cea7b0
> 0,      43200,      43200,      960,    15316, 0xaa040ae8
> 0,      44160,      44160,      960,    15356, 0xa13cfd43
> 0,      45120,      45120,      960,    15388, 0xf6a81182
> 0,      46080,      46080,      960,    15324, 0x72e4de3f
> 0,      47040,      47040,      960,    15252, 0x5d84b107
> 0,      48000,      48000,      960,    15216, 0xe9656c9b
> 0,      48960,      48960,      960,    15232, 0x6930b4a3
> 
> But you're right that it was also failing during decoding. Not sure how
> i missed or why i thought the framecrc output was the same. So nevermind
> my previous comment.