Re: [Libav-user] Is libav thread-safe?
Well, yes, you can call C from a C++ app. You need to mark the headers as C when you include them, but that's about it. Well, thanks for the help, but actually this isn't true. I tried this with the demuxing.c example and that didn't work. It sounds like you're trying to solve a problem that you don't have yet. Start with the basics - just getting going from a cold start in ffmpeg is enough trouble for most people, without trying to get clever. Actually I have already wasted several weeks or months of coding time doing what you suggested: assume ffmpeg/libav works the way you want it, then start coding. I think it's better to ask up front if libav is threadsafe before I spend a week implementing a multi-threaded app and then find out it can't possibly work because ffmpeg and libav are not thread-safe. I want to have multiple threads decoding different parts of the AVI file concurrently. No encoding will occur. Seems like it should be thread-safe. But I'd like to know for sure before I start coding. That's all. Ask questions first, code later. That stops me from complaining when libav doesn't do what I want. I'll just choose another route. On , Bruce Wheaton br...@spearmorgan.com wrote: On Oct 8, 2013, at 12:05 PM, James Board jpboa...@yahoo.com wrote: I want to create several pthreads in a C++ program (assuming you can call libav routines from a C++ program) that each call libav subroutines. Well, yes, you can call C from a C++ app. You need to mark the headers as C when you include them, but that's about it. Are the libav subroutines thread-safe? Specifically, can several pthreads open the same AVI file and decode different video frames concurrently? No, not really. At least, you'd have to lock the access entirely, which would make it sequential. You can use each context in one thread, and there are a few overall functions that need locking, such as choosing the right codecs for a file. I'm doing this so I can write a real-time video that can play the video forward and backwards, and the multiple threads will help decode and process each frame quickly so there will be no delay when I step through the video. Most codecs are multi-threaded by now - so there already are threads running to decode frames. You can set the number of threads you want a codec to use when you open it. There's a number of other things you could do... multiple codecs open etc. But with codecs that need B and P frames, you pretty much have to decode in order anyway, and file access is always going to be one at a time. It sounds like you're trying to solve a problem that you don't have yet. Start with the basics - just getting going from a cold start in ffmpeg is enough trouble for most people, without trying to get clever. Bruce ___ Libav-user mailing list Libav-user@ffmpeg.org http://ffmpeg.org/mailman/listinfo/libav-user___ Libav-user mailing list Libav-user@ffmpeg.org http://ffmpeg.org/mailman/listinfo/libav-user
Re: [Libav-user] Compile with g++
That's an example program written in C. There's nothing in the actual codebase (as opposed to the examples) that doesn't work in C++. Yes, I know it's a program written in C. As I stated before, I only used that example because everyone here already has a copy of it. The alternative would be for me to post my lengthy C++ code, which uses lots of thrid-part libraries, which nobody will be able to compile anyway). When I compile demuxing.c with g++ it gives me the same errors as when I add libav calls to my C++ app and then try to compile that with g++. So, if we can figure out why demuxing.c won't compile with g++, then we will probably figure out why my C++ app won't compile with g++. On Tuesday, October 8, 2013 9:25 PM, Bruce Wheaton br...@spearmorgan.com wrote: On Oct 8, 2013, at 11:12 AM, James Board jpboa...@yahoo.com wrote: I tried exactly that with the demuxing.c example. When I try to compile it with the C++ compiler, I get errors. When I compile with the C compiler, no errors. What do I need to do to get demuxing.c to compile with the C++ compiler in Linux? That's an example program written in C. There's nothing in the actual codebase (as opposed to the examples) that doesn't work in C++. Compile a C example as C. Bruce ___ Libav-user mailing list Libav-user@ffmpeg.org http://ffmpeg.org/mailman/listinfo/libav-user___ Libav-user mailing list Libav-user@ffmpeg.org http://ffmpeg.org/mailman/listinfo/libav-user
Re: [Libav-user] Compile with g++
demuxing.c is a C program, if you want to compile it with C++ (why?) you will have to convert it to C++, just as with any other C program. Yes, I know it's a program written in C. As I stated before, I only used that example because everyone here already has a copy of it. The alternative would be for me to post my lengthy C++ code, which uses lots of third-party libraries, which nobody will be able to compile anyway). When I compile demuxing.c with g++ it gives me the same errors as when I add libav calls to my C++ app and then try to compile that with g++. So, if we can figure out why demuxing.c won't compile with g++, then we will probably figure out why my C++ app won't compile with g++. (Nothing about this is FFmpeg specific.) This is the libav mailing list, not the fmpeg mailing list The issue is how to add libav calls to a c++ program. Carl Eugen On , James Board jpboa...@yahoo.com wrote: That's an example program written in C. There's nothing in the actual codebase (as opposed to the examples) that doesn't work in C++. Yes, I know it's a program written in C. As I stated before, I only used that example because everyone here already has a copy of it. The alternative would be for me to post my lengthy C++ code, which uses lots of thrid-part libraries, which nobody will be able to compile anyway). When I compile demuxing.c with g++ it gives me the same errors as when I add libav calls to my C++ app and then try to compile that with g++. So, if we can figure out why demuxing.c won't compile with g++, then we will probably figure out why my C++ app won't compile with g++. On Tuesday, October 8, 2013 9:25 PM, Bruce Wheaton br...@spearmorgan.com wrote: On Oct 8, 2013, at 11:12 AM, James Board jpboa...@yahoo.com wrote: I tried exactly that with the demuxing.c example. When I try to compile it with the C++ compiler, I get errors. When I compile with the C compiler, no errors. What do I need to do to get demuxing.c to compile with the C++ compiler in Linux? That's an example program written in C. There's nothing in the actual codebase (as opposed to the examples) that doesn't work in C++. Compile a C example as C. Bruce ___ Libav-user mailing list Libav-user@ffmpeg.org http://ffmpeg.org/mailman/listinfo/libav-user___ Libav-user mailing list Libav-user@ffmpeg.org http://ffmpeg.org/mailman/listinfo/libav-user
Re: [Libav-user] Is libav thread-safe?
On 10/9/13, James Board jpboa...@yahoo.com wrote: Well, yes, you can call C from a C++ app. You need to mark the headers as C when you include them, but that's about it. Well, thanks for the help, but actually this isn't true. I tried this with the demuxing.c example and that didn't work. It sounds like you're trying to solve a problem that you don't have yet. Start with the basics - just getting going from a cold start in ffmpeg is enough trouble for most people, without trying to get clever. Actually I have already wasted several weeks or months of coding time doing what you suggested: assume ffmpeg/libav works the way you want it, then start coding. I think it's better to ask up front if libav is threadsafe before I spend a week implementing a multi-threaded app and then find out it can't possibly work because ffmpeg and libav are not thread-safe. I want to have multiple threads decoding different parts of the AVI file concurrently. No encoding will occur. Seems like it should be thread-safe. But I'd like to know for sure before I start coding. That's all. Ask questions first, code later. That stops me from complaining when libav doesn't do what I want. I'll just choose another route. If you use different AVCodecContext it should be fine, otherwise it will crash. ___ Libav-user mailing list Libav-user@ffmpeg.org http://ffmpeg.org/mailman/listinfo/libav-user
Re: [Libav-user] Compile with g++
James Board jpboard2@... writes: (Nothing about this is FFmpeg specific.) This is the libav mailing list, not the fmpeg mailing list This is a mailing list about FFmpeg (that is why it is hosted on the FFmpeg server). Questions about how to convert a C program (that allows implicit type conversions which is why FFmpeg - and demuxing.c - does not contain explicit type conversions) into a C++ program (which needs explicit conversions) is not completely appropriate here afaict. Carl Eugen ___ Libav-user mailing list Libav-user@ffmpeg.org http://ffmpeg.org/mailman/listinfo/libav-user
Re: [Libav-user] Compile with g++
this is actually a FFmpeg e-mail list .. for multithreaded implementations you should have a look at av_lockmgr_register() Mihai, demuxing.c is a C program, if you want to compile it with C++ (why?) you will have to convert it to C++, just as with any other C program. Yes, I know it's a program written in C. As I stated before, I only used that example because everyone here already has a copy of it. The alternative would be for me to post my lengthy C++ code, which uses lots of third-party libraries, which nobody will be able to compile anyway). When I compile demuxing.c with g++ it gives me the same errors as when I add libav calls to my C++ app and then try to compile that with g++. So, if we can figure out why demuxing.c won't compile with g++, then we will probably figure out why my C++ app won't compile with g++. (Nothing about this is FFmpeg specific.) This is the libav mailing list, not the fmpeg mailing list The issue is how to add libav calls to a c++ program. Carl Eugen On , James Board jpboa...@yahoo.com wrote: That's an example program written in C. There's nothing in the actual codebase (as opposed to the examples) that doesn't work in C++. Yes, I know it's a program written in C. As I stated before, I only used that example because everyone here already has a copy of it. The alternative would be for me to post my lengthy C++ code, which uses lots of thrid-part libraries, which nobody will be able to compile anyway). When I compile demuxing.c with g++ it gives me the same errors as when I add libav calls to my C++ app and then try to compile that with g++. So, if we can figure out why demuxing.c won't compile with g++, then we will probably figure out why my C++ app won't compile with g++. On Tuesday, October 8, 2013 9:25 PM, Bruce Wheaton br...@spearmorgan.com wrote: On Oct 8, 2013, at 11:12 AM, James Board jpboa...@yahoo.com wrote: I tried exactly that with the demuxing.c example. When I try to compile it with the C++ compiler, I get errors. When I compile with the C compiler, no errors. What do I need to do to get demuxing.c to compile with the C++ compiler in Linux? That's an example program written in C. There's nothing in the actual codebase (as opposed to the examples) that doesn't work in C++. Compile a C example as C. Bruce ___ Libav-user mailing list Libav-user@ffmpeg.org http://ffmpeg.org/mailman/listinfo/libav-user ___ Libav-user mailing list Libav-user@ffmpeg.org http://ffmpeg.org/mailman/listinfo/libav-user
Re: [Libav-user] Compile with g++
On Wed, 9 Oct 2013 07:29:52 -0700 (PDT)
James Board jpboa...@yahoo.com wrote:
This is a mailing list about FFmpeg (that is why
it is hosted on the FFmpeg server). Questions
about how to convert a C program (that allows
implicit type conversions which is why FFmpeg
- and demuxing.c - does not contain explicit
type conversions) into a C++ program (which
needs explicit conversions) is not completely
appropriate here afaict.
Really? The title of the mailing list is Libav-user@ffmpeg.org.
I'm asking whether libav can be used in C++ programs, if anyone
uses libav in C++ programs, and what I need to do in order to
use libav in C++ programs. How can that be inappropriate?
Anyway, don't bother. I give up. You win.
You just need to wrap all you libav includes in extern C { }, like
this
#ifdef __cplusplus
extern C {
#include libavutil/avutil.h
#include libavutil/mathematics.h
#include libavutil/imgutils.h
#include libavutil/samplefmt.h
#include libavutil/time.h
#include libavcodec/avcodec.h
#include libavformat/avformat.h
#include libswscale/swscale.h
}
#endif // __cplusplus
As for UINT64_C you can do this
#ifndef INT64_C
#define INT64_C(c) (c ## LL)
#define UINT64_C(c) (c ## ULL)
#endif // INT64_C
I' m using libav in many of my projects which include other third
party libraries. The above are the only things required.
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Re: [Libav-user] Compile with g++
Michael Chisholm chisholm@... writes: So my point to all this is, the ffmpeg-2.0.1 headers aren't completely C++-friendly I don't think this is correct as such: The headers are neither C++-friendly nor C++-unfriendly, they are simply C headers and exactly the same limitations apply than when using any other (non-trivial) C headers from a C++ program. The fact that some explicit casting is necessary in C++ is completely orthogonal to the C++- friendliness of the FFmpeg headers afaict. Do I understand correctly that you cannot use the av_ts2timestr() macro from C++ but that it is not used inside of FFmpeg in a way that makes using one of the libraries or one of the headers impossible? (If you know how to fix it, consider sending a patch, assuming it does not slow down the macro for C, such a change is useful imo.) Carl Eugen ___ Libav-user mailing list Libav-user@ffmpeg.org http://ffmpeg.org/mailman/listinfo/libav-user
[Libav-user] Extract frames in raw RGB formats
Hi I am wondering if anyone can help me how can i use ffmpeg to extract frames in raw RGB image forma. The following code does not work: ffmpeg -i foo.mp4 -r 1 -s 320x240 -f image2 foo-%03d.rgb ___ Libav-user mailing list Libav-user@ffmpeg.org http://ffmpeg.org/mailman/listinfo/libav-user
