I have a series of jpegs,I would like to pack and compress them to a Video.
I use tool mpeg streamclip, but it double the whole play time.
If I have 300 jpegs, set fixed fps 30, I expect to get a video of 10s length . but using stream clip I get a 20s long video.
One answer is to get someone who understands programming. The programming APIs (application interfaces, the way client programs call libraries) to the lig libraries like ffmeg have ways in which frame rate can be controlled, and it's usually quite a simple matter to modify a program to produce fewer intermediate frames if you are creating a video from a list of JPEGs.
But the best answer is probably to find a tool that supports what you want to do. That's not a question to ask a programmer especially. Ask someone who knows about video editing. (It would take me about two days to write such a tool from scratch on top of my own JPEG codec and ffmpeg, so obviously I can't do it in response to this question, but that's roughly the level of work you're looking at).
Related
After searching on various search engines, and also here, there is very little information applicable to my situation.
Basically I want to make a program in C that does the following:
Open an Audio File (flac Mp3 and wav, to represent a bit of variety)
Filter and cut out a specific set of frequencies (for Example 4000-5200hz, the frequencies should be entered upon inquiry)
Save the new file (without the filtered frequencies) in the same format as the input file.
Things that would be of interest to me:
Open-Source examples of software that does the same or a similar thing, preferably in C
ANY literature on audio programming in C
Explanations on how the different formats are structured, any sources appreciated
Ps.: I apologise if some parts of the question can be easily googled, but I tried, and there wasn't anything that described this well in detail.
Thanks a lot!!
Answers:
FFmpeg does a lot of audio slicing and dicing, and it's written in pure C. It's pretty big, though, and might be difficult to digest in one go.
"Audio programming" is a bit vague. But from the rest of your question, it sounds like you want to open an audio file from disk, apply some transformations to the audio, and write the data to a new file. (Other areas under the "audio programming" umbrella would include accessing platform-specific APIs to read from a microphone and write audio to an output device).
Broad topic again, but we'll start simple.
I suggest getting (or generating) a .WAV file to start with. WAV files are probably the simplest audio files to read and write manually. Here is a page that describes what you need to know about the WAV format.
Pulse code modulation (PCM) is the simplest audio format to work with since you don't need to worry about decompressing it first. Here is a page (that I wrote) describing different PCM formats.
As for filtering and cutting different frequencies, I think what you're looking for would be low-pass, high-pass, or band-pass filters.
I hope that helps you get started. Ask more questions here on Stack Overflow as needed.
I'm about to start working on a project for Minix 3 (in C).
My idea is to create some kind of a music player. I want to be able to read files (WAV) and then convert them to a stream of frequencies send to the Timer 2.
Since, has far as I know, there is no easy way to read real music files, I thought of approaching the real frequencies in a block, to a simple mono curve sent to the timer 2.
Ok, issues:
I read and learned, how to read wav headers, but, I can't find anywhere what's the meaning of the data in the data chunk. How should I interpret it?
My initial idea was to make a real music player, but, in my classes we didn't learned how to work with the sound board in Minix 3. Is there some tutorial, anything where I can learn it?
As far as I could realize, C as already a library to manage sound (BASS). Can and How I install it in Minix 3?
Finally, Is it a way to make all this simpler?
A WAV files is not a "stream of frequencies". It contains a series of samples formatted according to the information written in the header.
In best of worlds you just set up your sound card to handle the data format specified in the header, then you just have to keep providing the raw data in the "DATA" chunks to your sound cards data buffers.
How this is done in Minix 3 is out of bounds for this answer (I just don't know how Minix handles sound at all) but I'm sure it will be to great help for understanding the basics of digital audio.
I'm creating a simple midi based game in C and I am wondering if there are any libraries to load a midi file, play and also manipulate it by getting the note values.
Thanks in advance!
Check SDL. More especifically, SDL_mixer.
Description:
SDL_mixer is a sample multi-channel audio mixer library.
It supports any number of simultaneously playing channels of 16 bit stereo audio, plus a single channel of music, mixed by the popular MikMod MOD, Timidity MIDI, Ogg Vorbis, and SMPEG MP3 libraries.
If you want to manipulate the MIDI and process its contents yourself rather than just playing it, SDL_Mixer might not be what you want. In this case I would just read the spec and write your own code. MIDI is an extremely simple format and you can probably write whatever code you need in 15 minutes or so... :-)
I realize this question has already been answered, but I would have to agree with #R.. in that SDL is probably overkill for what you are trying to do. You should also take a look at jdksmidi, a much smaller MIDI library written in C++.
What I wish to do is to "split" an .mp3 into two separate files, taking duration as an argument to specify how long the first file should be.
However, I'm not entirely sure how to achieve this in C. Is there a particular library that could help with this? Thanks in advance.
I think you should use the gstreamer framework for this purpose. So you can write an application where you can use existing plugins to do this job. I am not sure of this but you can give it a try. Check out http://gstreamer.freedesktop.org/
For queries related to gstreamer: http://gstreamer-devel.966125.n4.nabble.com/
If you don't find any library in the end, then understand the header of a mp3 file and divide the original file into any number of parts and add individual headers to them. Its not gonna be easy but its possible.
It can be as simple as cutting the file at a position determined by the mp3 bitrate and duration requested. But:
your file should be CBR - that method won't work on ABR or VBR files, because they have different densityes
your player should be robust enough not to break if it gets partial mp3 frame at a start. Most of the playback libraries will handle mp3s split that way very gracefully.
If you need more info, just ask, I am on the mobile and can get you more info later.
If you want to be extra precise when cutting, you can use some library to parse mp3 frame headers, and then write frames that you need. That way, and the way mentioned before, you'll get only frame alignment as a minimum, and you have to live with thaty and that's 40ms.
If that isn't enough, you must decode mp3 to PCM, split at sample boundary, then recompress to mp3 again.
Good luck
P.s.
When you say split, I hope you don't expect them to play one after another with no audible 'artifacts'. Mp3 frames aren't self-sufficient, as they carry information from the frame before.
Consider the following file:
-rw-r--r-- 1 user user 470886479 2009-12-15 08:26 the_known_universe.png
How would you scale the image down to a reasonable resolution, using no more than 4GB of RAM?
For example:
$ convert -scale 7666x3833 the_known_universe.png
What C library would handle it?
Thank you!
I believe libpng has a stream interface. I think this can be used to read parts of the image at a time; depending on the image file you might be able to get the lines in order. You could then shrink each line (e.g. for 50% shrinking, shrink the line horizontally and discard every second line) and write to an output file.
Using libpng in C can take a fair amount of code, but the documentation guides you through it pretty well.
http://www.libpng.org/pub/png/libpng-1.2.5-manual.html#section-3.8
You could try making a 64 bit build of ImageMagick or seeing if there is one. My colleague wrote a blog with a super-simple png decoder (assumes you have zlib or equivalent) so you can kind of see the code you'd need to roll your own.
http://www.atalasoft.com/cs/blogs/stevehawley/archive/2010/02/23/libpng-you-re-doing-it-wrong.aspx
You would need to do the resample as you're reading it in.
I used cximage a few years ago. I think the latest version is at
http://www.xdp.it/cximage.htm
after moving off of CodeProject.
Edit: sorry, it's C++ not C.
You could use an image processing library that is intended to do complex operations on large (and small) images. One example is the IM imaging toolkit. It links well with C (but is implemented at least partly in C++) and has a good binding to Lua. From the Lua binding it should be easy to experiment.
libvips is comfortable with huge images. It's a streaming image processing library, so it can read from the source, process, and write to the destination simultaneously and in parallel. It's typically 3x to 5x faster than imagemagick and needs very little memory.
For example, with the largest PNG I have on my laptop (1.8gb), I can downsize 10x with:
$ vipsheader huge.png
huge.png: 72000x72000 uchar, 3 bands, srgb, pngload
$ ls -l huge.png
-rw-r--r-- 1 john john 1785845477 Feb 19 09:39 huge.png
$ time vips resize huge.png x.png 0.1
real 1m35.279s
user 1m49.178s
sys 0m1.208s
peak RES 230mb
Not fast, but not too shabby either. PNG is rather a slow format, it would be much quicker with TIFF.
libvips is installable by most package managers (eg. homebrew on macOS, apt on Debian), there's a Windows binary, and it's free (LGPL). As well as the command-line, there are bindings for C, C++, Python, Ruby, Lua, node, PHP, and others.
Have you considered exploring pyramid based images? Imagine a pyramid where the image is divided up in multiple layers, each layer with a different resolution. Each layer is split up into tiles.
This way you can display a zoomed out version of the image, and also a zoomed in partial view of the image, without having to re-scale.
See the Wikipedia entry.
One of the original formats was FlashPix, which I wrote a renderer for.
I've also created a new format of a pyramid converter and renderer, which was used for a medical application. An actual scanner would produce 90GB+ scans of a slice of an organ for cancer research.
The algorithm of the converter was actually pretty tricky to get efficient, to produce the pyramid images efficienty. Believe it or not, it was actually Java based, and it performed much better than you'd think. It used multithreading. Benchmarking showed it was unlikely that a C version would do a whole lot better. This was 6ish years ago. The original renderer I did over 10 years ago.
You don't hear anything about pyramid based images anymore these days. But it's really the only efficient way to produce scaled images on demand without having to generate cached scaled versions.
Jpeg2000 may or may not have an optional pyramid feature as well.
I recall that ImageMagick's supporter formats and conversions perhaps, include FlashPix.
Googling for "image pyramid" reveals some interesting results. Bring back some memories ;-)
If you can move it to a 64-bit OS you can open it as a memory mapped file or equivalent and use pretty much any library you want. It won't be fast, and may need the increase of the page/swap file (depending on the OS and what else you want to do with it) but in return you won't be limited to streaming libraries so you'll be able to do more operation before going into resolution reduction or slicing.