i'm a bit at loss here. My goal is to merge two video files (which might be of different file formats) and i'm already using libffmpeg for other simple tasks. I thought libffmpeg exposed some kind of function to merge files, but i can't find it.
I found these pages on the documentation that might be relevant: http://ffmpeg.org/doxygen/trunk/structConcatStream.html and http://ffmpeg.org/doxygen/trunk/group__lavf__encoding.html
I'm not sure if this is really relevant though? Can anybody point me in the right direction? Do i need to use FFmpeg muxing and manually joins streams? Is there any example that can explain to me what i should do? thanks!
For those looking for an example, i ended up using
How to use libavformat to concat 2 video files with same codec (re-muxing)?
there's a nice snippet and it works very well
Use ffmpeg to open file 1, start reading frames, converting to target format, and writing to the output file. When there are no more frames, close file 1 (leave output open). Open file 2, start reading frames, converting to target format, and writing to the output file. When there are no more frames, close file 2 and close output.
Merged and formats reconciled.
Related
How can I, using a function, library, whatever I have to, concatenate two .wav files? The input should be the absolute paths, and the output an audio file created and placed (not just played) somewhere, it doesn't really matter where.
I am writing a Mac command line application in XCode 6.
The .wav file format is a very simple format, consisting of the fixed header that defines the audio file's properties; namely the endian-ness, the number of channels, and the sampling rate. Its documentation is widely defined on the intertubes.
Off the top of my head I don't recall if any common library offers a convenient way to do this (it's worth looking through libsndfile's API documentation, for something that would fit the bill).
In any case, it shouldn't be too tough to read the headers of both WAV files, to check their format, and then create the output file. If both WAV files have the same endian-ness, number of channels, and sampling rate, the procedure is trivial, otherwise you will have to resample/remix at least one of the files.
There is a very simple, lightweight and mature open source C API library for reading-writing several common audio file formats. I haven't worked with it for a while, if I remember well, it has routines for opening a sound file for writing, seeking the end, appending data from another file and updating the header. I hope this can help.
I've seen a lot of examples of i/o with text files I'm just wondering if you can do the same with other file types like mp3's, jpg's, zip files, etc..?
Will iostream and fstream work for all of these or do I need another library? Do I need a new sdk?
It's all binary data so I'd think it would be that simple. But I've been unpleasently surprised before.
Could I convert all files to text or binary?
It depend on what you mean by "work"
You can think of those files as a book written in Greek.
If you want to just mess with binary representation (display text in Greek on screen) then yes, you can do that.
If you want to actually extract some info: edit video stream, remove voice from audio (actually understand what is written), then you would need to either parse file format yourself (learn Greek) or use some specialized library (hire a translator).
Either way, filestreams are suited to actually access those files data (and many libraries do use them under the hood)
You can work on binary streams by opening them with openmode binary :
ifstream ifs("mydata.mp3", ios_base::binary);
Then you read and write any binary content. However, if you need to generate or modify such content, play a video or display a piture, the you you need to know the inner details of the format you are using. This can be exremely complex, so a library would be recomended. And even with a library, advanced programming skills are required.
Examples of open source libraries: ffmpeg for usual audio/video format, portaudio for audio, CImg for image processing (in C++), libpng for png graphic format, lipjpeg for jpeg. Note that most libraries offer a C api.
Some OS also supports some native file types (example, windows bitmaps).
You can open these files using fstream, but the important thing to note is you must be intricately aware of what is contained within the file in order to process it.
If you just want to open it and spit out junk, then you can definitely just start at the first line of the file and exhaustively push all data into your console.
If you know what the file looks like on the inside, then you can process it just as you would any other file.
There may be specific libraries for processing specific files, but the fstream library will allow you to access any file you'd like.
All files are just bytes. There's nothing stopping you from reading/writing those bytes however you see fit.
The trick is doing something useful with those bytes. You could read the bytes from a .jpg file, for example, but you have to know what those bytes mean, and that's complicated. Usually it's best to use libraries written by people who know about the format in question, and let them deal with that complexity.
I'm trying to write a JPEG file.
After I acquire the raw image and processing it by DCT, quantization and huffman coding, I would like to save it in the correct format. I couldn't find any libraries that help me to write proper header file, insert the two tables that I used (huffman and quantization), so I started writing everything by myself.
I started with the SOI marker, frame header and so on, but when I try to open the JPEG image with a viewer, it shows nothing, even in the properties. There's no information shown (e.g. the image dimension), even if I insert this info like written in the official documentation.
How can I write a proper JPEG header?
P.S
I use C++ and Visual Studio 2010.
Simple answer - it's complicated.
I would start with libjpeg and use it to just give you the approriate header. You can also use it as a reference for what the internal header structs look like
I am interesting to do some transformation, like change one color to another, count all used colors, and resize image. I DO NOT want to use any exist library, I would like write myslelf all code.
Summing up: How could I open BMP file and change it?
Start by learning the bitmap file format. It is very easy to understand and implement.
You can get any file format by going to www.wotsit.org and searching for the file type you want. In your case BMP. There are different types of bitmaps so you can figure out which ones you want to implement.
I would start with reading some documentation. Maybe go to Wikipedia for an overview.
You need to read in the binary file, figure out what all the bits mean, do your transformation, and write out a new binary file. For figuring out the format of various binary files, wotsit is the best resource I've found. They have links to 5 specs for BMP format files.
Greetings all,
I am currently a rising Sophomore (CS major), and this summer, I'm trying to teach myself C++ (my school codes mainly in Java).
I have read many guides on C++ and gotten to the part with ofstream, saving and editing .txt files.
Now, I am interested in simply importing an image (jpeg, bitmap, not really important) and renaming the aforementioned image.
I have googled, asked around but to no avail.
Is this process possible without the download of external libraries (I dled CImg)?
Any hints or tips on how to expedite my goal would be much appreciated
Renaming an image is typically about the same as renaming any other file.
If you want to do more than that, you can also change the data in the Title field of the IPTC metadata. This does not require JPEG decoding, or anything like that -- you need to know the file format well enough to be able to find the IPTC metadata, and study the IPTC format well enough to find the Title field, but that's about all. Exactly how you'll get to the IPTC metadata will vary -- navigating a TIFF (for one example) takes a fair amount of code all by itself.
When you say "renaming the aforementioned image," do you mean changing metadata in the image file, or just changing the file name? If you are referring to metadata, then you need to either understand the file format or use a library that understands the file format. It's going to be different for each type of image file. If you basically just want to copy a file, you can either stream the contents from one file stream to another, or use a file system API.
std::ifstream infs("input.txt", std::ios::binary);
std::ofstream outfs("output.txt", std::ios::binary);
outfs << insfs.rdbuf();
An example of a file system API is CopyFile on Win32.
It's possible without libraries - you just need the image specs and 'C', the question is why?
Targa or bmp are probably the easiest, it's just a header and the image data as a binary block of values.
Gif, jpeg and png are more complex - the data is compressed