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Shaun_Marko
Beginner
75 Views

MPEG2 encoder segfault

Hello,

I'm new to IPP, so I'm probably missing something rather simple. Attached is test code that crashes when instantiating a structure which contains an MPEG2VideoEncoder object and an MPEG2EncoderParam object. The debugger indicates the crash occurs in the MPEG2EncoderParams constructor when it assigns default values to the IntraQMatrix data member:

lnet@I5-desktop$ idbc ./mp2
Intel Debugger for applications running on IA-32, Version 12.0, Build [1.3842.2.129]
------------------
object file name: ./mp2
Reading symbols from /home/lnet/work/mp2/mp2...done.
(idb) run
Starting program: /home/lnet/work/mp2/mp2
[New Thread 3077773568 (LWP 24206)]
[New Thread 3077773568 (LWP 24206)]
Program received signal SIGSEGV
UMC::MPEG2EncoderParams::MPEG2EncoderParams (this=0x87e50a8) at /home/lnet/work/ipp-samples/audio-video-codecs/codec/mpeg2_enc/src/umc_mpeg2_enc_params.cpp:117
117 IntraQMatrix = DefaultIntraQuantMatrix;
(idb) where
#0 0x0804cbdb in UMC::MPEG2EncoderParams::MPEG2EncoderParams (this=0x87e50a8) at /home/lnet/work/ipp-samples/audio-video-codecs/codec/mpeg2_enc/src/umc_mpeg2_enc_params.cpp:117
#1 0x0804f729 in UMC::MPEG2VideoEncoderBase::MPEG2VideoEncoderBase (this=0x0) at /home/lnet/work/ipp-samples/audio-video-codecs/codec/mpeg2_enc/src/umc_mpeg2_enc.cpp:24
#2 0x0804ec46 in UMC::MPEG2VideoEncoder::MPEG2VideoEncoder (this=0x340) at /home/lnet/work/ipp-samples/audio-video-codecs/codec/mpeg2_enc/src/umc_mpeg2_video_encoder.cpp:35
#3 0x0804c801 in Foo::Foo (this=0x87e4d10) in /home/lnet/work/mp2/mp2
#4 0x0804c798 in main (argc=1, argv=0xbfac5304) at /home/lnet/work/mp2/mp2.cpp:15
#5 0x005a6ce7 in __libc_start_main () in /lib/libc-2.12.1.so
#6 0x0804c6a1 in _start () in /home/lnet/work/mp2/mp2
(idb)

I may be barking up the wrong tree, but it appears the IntraQMatrix should be 16-byte aligned and it is not:
(idb) print &IntraQMatrix
$2 = (Ipp16s (*)[64]) 0x87e5178
(idb) print &IntraQMatrix%16
$3 = 8

If the Foo structure containing the MPEG2VideoEncoder and MPEG2EncoderParams objects is created on the stack rather than allocated from the heap, the crash does not occur.

I'm running the code on a core I5 machine with 32-bit Ubuntu 10.10 OS:
uname: Linux I5-desktop 2.6.35-22-generic #33-Ubuntu SMP Sun Sep 19 20:34:50 UTC 2010 i686 GNU/Linux
Compiler: Intel C++ Compiler XE for applications running on IA-32, Version 12.0.0.084 Build 20101006
ipp samples: linux 7.0.1.029

Any pointers would be greatly appreciated.

-Shaun





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9 Replies
Vladimir_Dudnik
Employee
75 Views

Hi Shaun,

please check with audio-video-codecs sample how to use UMC object and structures. We do not see crashes in compiled UMC sample code.

Regards,
Vladimir
Shaun_Marko
Beginner
75 Views

Hi Vladmir,

Thanks for the reply. Unfortunately, I'm seeing a crash with the sample code:

lnet@I5-desktop$ idbc ./umc_video_enc_con
Intel Debugger for applications running on IA-32, Version 12.0, Build [1.3842.2.129]
------------------
object file name: ./umc_video_enc_con
Reading symbols from /home/lnet/test/umc_video_enc_con...done.
(idb) run -y img -o video.mpg mpeg2.par
Starting program: /home/lnet/test/umc_video_enc_con
[New Thread 3079510272 (LWP 7779)]
[New Thread 3079510272 (LWP 7779)]
Program received signal SIGSEGV
UMC::MPEG2EncoderParams::MPEG2EncoderParams (this=0x9e11628) at /home/lnet/work/ipp-samples/audio-video-codecs/codec/mpeg2_enc/src/umc_mpeg2_enc_params.cpp:117
117 IntraQMatrix = DefaultIntraQuantMatrix;

My application worked with the 11.1 version of the C++ professional compiler for linux that I used to evaulate the product. The license my company purchased was for the composerxe-2011 version. After installing that and rebuilding with the licensed compiler, may application segfaults.

-Shaun

Chao_Y_Intel
Employee
75 Views


Shaun,

Can you provide the par file, and related input YUV file?

thanks,
Chao

Shaun_Marko
Beginner
75 Views

The sample application segfaults when using just the mpeg2.par included with the samples, like this:
./umc_video_enc_con m2 ../../application/umc_video_enc_con/mpeg2.par video.mpg
Segmentation fault

A program as simple as this segfaults in the same location in the MPEG2EncoderParams constructor:

#include
#include
#include
#include
#include
#include
#include

using namespace UMC;


int main(int argc, char **argv)
{
MPEG2VideoEncoder *encoder = new MPEG2VideoEncoder;
MPEG2EncoderParams *params = new MPEG2EncoderParams;

std::cout << params->gopSize << std::endl;

return 0;
}



-Shaun

Chao_Y_Intel
Employee
75 Views



Shaun,

The code in the line looks fine: codecs/codec/mpeg2_enc/src/umc_mpeg2_enc_params.cpp:117

117 IntraQMatrix = DefaultIntraQuantMatrix;

If you use GCC to build the sample, how does it work for you?

Thanks,
Chao

Shaun_Marko
Beginner
75 Views

Hi Chao,

The GCC build of umc_video_enc_con appears to work fine:

$ ./umc_video_enc_con -n 100 -i /dev/urandom ../../application/umc_video_enc_con/mpeg2.par video.mpg
Starting MPEG2 encoding /dev/urandom to file video.mpg
Source video width = 352, height = 288, frameRate = 24.00
Max frames to encode = 100
Encoding bit rate = 5300000 bits per second
0.10.20.30.40.50.60.70.80.90.100.
Summary:
Num frames encoded = 100
Encoding Time = 0.15 sec, 669.73 fps
Overall Time = 1.97 sec, 50.82 fps
Average CPU usage = 0.00%
Encoded Size = 2759608 bytes
Compression Ratio = 5.51
EncodedSize/ExpectedSize = 1.00

Incidentally, this test was run on a fresh install of Intel ComposerXE 2011 for linux and the latest IPP samples on Ubuntu 10.4 (32-bit). The ICC build of the umc_video_enc_con sample application still segfaults:

$ ./umc_video_enc_con -n 100 -i /dev/urandom ../../application/umc_video_enc_con/mpeg2.par video.mpg
Segmentation fault

Thanks for your help.

-Shaun


Shaun_Marko
Beginner
75 Views

Chao,

Have you been able to reproduce this issue? I provided a simple test case that fails on my Linux Ubuntu 10.4 system.

-Shaun
Chao_Y_Intel
Employee
75 Views


Shaun,

I have a test here. I can see the error you report here. The problem seems that the compiler is generating the incorrect code on the following line ( This line of the code looks fine in the source)

117 IntraQMatrix = DefaultIntraQuantMatrix;

Since GCC compiler can work well, I also tried to compile the source with O0 option ( in the Makefile change CFLAGS = -Wall -O0 fPIC), the sample code also works fine. So possibly you can use -O0 as workaround for build MPEG2 encoder.

Thanks,
Chao

Shaun_Marko
Beginner
75 Views

Chao,

Thanks for the follow up. I'll run with the GCC compiler or the -O0 optimizations on the Intel compiler until this problem is resolved. Thanks again.

-Shaun
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