So... I'm dealing with a system that has input data coming in buffers (i.e. NOT a file). I want to determine which decoder to create to decompress an audio stream (MP3, WAV, OGG, ...) So obviously I do not know the input format.
I found out that I could determine the format using the av_probe_input_format[23]() functions. That part works great, I get a format pointer that matches the files that I use as input.
AVInputFormat * format(av_probe_input_format3(&pd, true, &score));
I can print the format->name and format->long_name and these are the correct type (so the detection is working as expected).
Now, I'm trying to understand how to convert that AVInputFormat * into a AVCodec * so I can call avcodec_alloc_context3(codec) to create the actual audio decoder.
I found a couple of functions, which I used like so:
AVCodecID const codec_id(av_codec_get_id(format->codec_tag, format->raw_codec_id));
AVCodec * codec(avcodec_find_decoder(codec_id));
Problem 1. the raw_codec_id field is marked as "private" (should not access/use anywhere in your client's code).
Problem 2. the first function always returns AV_CODEC_ID_NONE (0) so of course the second call fails each time.
Am I doing something wrong? Is there is way to instead create a generic decode that will automatically detect the type of audio I have as input? (that is, would that be the only way to make that work?)
Okay, so the fact is that trying to use these functions directly is pretty much futile. The problem I have with the design is that it forces me to actually have a callback and that callback forces me to have a thread (i.e. I have to somehow feed data from a stream, not a file or such!)
So I can use the avformat_open_input() as mentioned by Gyan, only I have to have my own AVIOContext. I was hoping I could just call functions with my incoming data and avoid the pipeline concept. The issue here is some background processes could be servers that use fork() and thus you need to be really careful (i.e. fork() is not friendly with threads).
I'm using Boosts Generic Image Library. I'm being given a string representation of an image. After decoding it, could I directly make an Image or View object with that data? Or would I need to write the data to the computer as example.png and use GIL's read_image functions? The documentation mentions dynamic images but still takes a filename as a parameter to the i/o functions.
I would ideally be looking for a function that takes a string or byte array as a parameter rather than the image name to be loaded from disk. Something like GDI+ FromStream. I see that the documentation says "All functions take the filename or a device as the first parameter. A device could be a FILE*, std::ifstream, and TIFF*." Maybe it is possible to edit the contents of an ifstream to have the image data, not sure if this is actually possible though.
RESOLVED: Problem was primarily with the simulink blockset that was reading in the UDP packet rather than data transmission.
I am trying to send a 20 byte numerical array out of a c++ program by using winsock. The issue I am running into is data packaging, in the end I want each number in the array to go out as its own byte so that my simulink model that is receiving these values does not need an additional processing script.
My array contains 14 boolean values (0|1) and then 6 values that range from -100 to 100. These are reporting the status of a controller input. for example the array would look like
int array msgint[20] = [1,0,1,0,0,1,1,0,0,0,0,0,0,0,50,80,-90,40,90,-20];
I have tried using typecasting and sending multiple strings but all just appear to rearrange the gibberish I am getting or cause a socket error. Currently my sendto function looks like
sendto(sd,message,80,0,(struct sockadd *) &server,server_length)
I know this line works as the packet makes it through it just does not appear as I would like it to. In the send to, message is the formatted string I am trying to create to properly send all of contents of the array. Currently is is arbitrary and has little significance I have it in for debugging purposes essentially.
you are starting at the wrong point. Network communications should start with the design of the wire protocol.
How will you represent something on the wire. Binary or text. Most 'modern' protocols use text (json or xml). A few years ago binary was hot (asn1/ber/der). I suggest json
Then how will you wrap up the payload. Do you need to say 'here is a set of xxxs. now here is a set of yyyys'. I dont know what you are doing so its hard to say what you need
If you want to send 20 bytes, and you know that every integer value in your array will be in the [-100, +100] range, you should not use the int type, which usually contains either 32-bit or 64-bit values on modern platforms.
You might instead want to use the char type, which usually represents a 8-bit value.
For even more certainty, if you can use C++11 features, you should use the <cstdint> header, which defines the int8_t type, guaranteed to be a signed 8-bit type. See http://en.cppreference.com/w/cpp/types/integer.
Your array should look like:
#include <cstdint>
std::int8_t msgint[20] = {1,0,1,0,0,1,1,0,0,0,0,0,0,0,50,80,-90,40,90,-20};
or
char msgint[20] = {1,0,1,0,0,1,1,0,0,0,0,0,0,0,50,80,-90,40,90,-20};
and your sendto will be:
sendto(sd,msgint,20,0,(struct sockadd *) &server,server_length);
"in the end I want each number in the array to go out as its own byte"
Then change your array to
char msgint[20] = ...
I am attempting to create an edit box that allows users to input text. I've been working on this for some time now and have tossed around different ideas. Ultimately, the one I think that would offer the best performance is to load all the characters from the .ttf (I'm using SDL to manage events, windows, text, and images for openGL) onto their own surface, and then render those surfaces onto textures one time. Then each frame, I can just bind an appropriate texture in the appropriate location.
However, now I'm thinking how to access these glyphs. My limited bkg would say something like this:
struct CharTextures {
char glpyh;
GLuint TextureID;
int Width;
int Height;
CharTextures* Next;
}
//Code
CharTexture* FindGlyph(char Foo) {
CharTextures* Poo = _FirstOne;
while( Poo != NULL ) {
if( Foo == Poo->glyph ) {
return Poo;
}
Poo = Poo->Next;
}
return NULL;
}
I know that will work. However, it seems very wasteful to iterate the entire list each time. My scripting experience has taught me some lua and they have tables in lua that allow for unordered indices of all sorts of types. How could I mimic it in C++ such that instead of this iteration, I could do something like:
CharTexture* FindGlyph(char Foo) {
return PooPointers[Foo]; //somehow use the character as a key to get pointer to glyph without iteration
}
I was thinking I could try converting to the numerical value, but I don't know how to convert char to UTF8 values and if I could use those as keys. I could convert to ascii but would that handle all the characters I would want to be able to type? I am trying to get this application to run on mac and windows and am not sure about the machine specifics. I've read about the differences of the different format (ascii v unicode v utf8 v utf16 etc)... I understand it has to do with bit width and endianness but I understand relatively little about the interface differences between platforms and implications of said endianness on my code.
Thank you
What you probably want is
std::map<char,CharTexture*> PooPointers;
using the array access operator will also use some search in the map behind the scene, but optimized.
What g-makulik has said is probably right. The map may be what you're after. To expand on the reply, maps are automatically sorted base on the key (char in this case) and so lookups based on the character is extremely quick using
CharTexture* pCharTexture = PooPointers[char];
If you want a sparse data structure where you don't predefine the texture for each character.
Note that running the code above where an entry doesn't exist will create a default entry in the map.
Depending on your general needs you could also use a simple vector if generalized sorting isn't important or if you know that you'll always have a fixed number of characters. You could fill the vector with predefined data for each possible character.
It all depends on your memory requirements.
I am trying to write a program that allows for uses to traverse the contents of a SD card with buttons on a touch screen (assume there is only one level of files; aka no folders). However, I am finding it impossible to get a "list" of all the files on the SD card:
I can't just create an array of stringsor char* because I don't know the number
of files on the card. Besides, I want the container to be dynamic if
possible.
I can't create a vector because Arduino doesn't recognize std::vector
or vector even when I have C++ for Arduino.
Searching google produces new does not exist in Arduino's C++
I could use malloc (or new), but that would involve me creating my own container class. As interesting as that may be, the goal of what I am doing is not to implement a dynamic container class.
Have I missed something major in my search for such a function?
I recommend you look at my example MP3 File Player and the Web Player.
There are TWO issues:
1) You need to approach this from the point of view appreciating the Arduino does not have enough resources (SRAM) to hold a list of entire SdFAT's directories. Hence my approach was to use the users console for retaining the list. It dumps the directories contents to the console, along with a corresponding number. From which the user could select the number they wish to enter. Similarly the Web Player does the same thing, but when generating the HTML, it generates a link pointing to the corresponding listed item. Hence the list is stored on the console being either the Browser or Serial Monitor.
2) The default provided SD library is not sufficient to do what you want. Recently Arduino incorporated Bill Greiman’s SdFatLib as the under the hood class. But limited it. Where using Bill’s native SdFat library allows you the use of additional methods to access individual objects, such as getFilename(), not available in SD. This is necessary when going through the directory. The sd.ls(LS_DATE | LS_SIZE) will only dump directly to serial. Where you need to use access the individual files themselves. As show below or in actual code
SdFile file;
char filename[13];
sd.chdir("/",true);
uint16_t count = 1;
while (file.openNext(sd.vwd(),O_READ))
{
file.getFilename(filename);
Serial.print(count);
Serial.print(F(": "));
Serial.println(filename);
count++;
}
file.close();
Additionally there are buried public methods accessible by references as show in WebPlayer’s ListFiles() function, to get more discrete handling of the files.