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diff --git a/www/devmaster/lesson6.html b/www/devmaster/lesson6.html index 3a0c5ee..36e3660 100644 --- a/www/devmaster/lesson6.html +++ b/www/devmaster/lesson6.html @@ -32,16 +32,17 @@ OpenAL Tutorials from DevMaster.net. Reprinted with Permission.<br> <p align="right" class="ArticleAuthor">Author: <a href="mailto:[email protected]">Jesse Maurais</a><br> Adapted For Java By: <a href="mailto:[email protected]">Athomas Goldberg</a></p> -<p>We've been doing some pretty simple stuff up until now that didn't require - us to be very precise in the way we've handled things. The reason for this is - that we have been writing code for simplicity in order to learn easier, rather - that for robustness. Since we are going to move into some advanced stuff soon - we will take some time to learn the proper ways. Most importantly we will learn - a more advanced way of handling errors. We will also reorganize the way we have - been loading audio data. There wasn't anything wrong with our methods in particular, - but we will need a more organized and flexible approach to the process.</p> -<p>We will first consider a few functions that will help us out a lot by the time - we have finished.</p> +<p align="justify">We've been doing some pretty simple stuff up until now that + didn't require us to be very precise in the way we've handled things. The reason + for this is that we have been writing code for simplicity in order to learn + easier, rather that for robustness. Since we are going to move into some advanced + stuff soon we will take some time to learn the proper ways. Most importantly + we will learn a more advanced way of handling errors. We will also reorganize + the way we have been loading audio data. There wasn't anything wrong with our + methods in particular, but we will need a more organized and flexible approach + to the process.</p> +<p align="justify">We will first consider a few functions that will help us out + a lot by the time we have finished.</p> <pre class=code><font color="#0000FF"><span class=codeComment><font color="#006600">/** * 1) Identify the error code. * 2) Return the error as a string. @@ -99,13 +100,13 @@ public static int </font>loadALBuffer(String path) <font color="#0000FF">throws< <font color="#0000FF">private static</font> Vector buffers = <font color="#0000FF">new</font> Vector(); <span class=codeComment><font color="#006600">// Holds all loaded buffers.</font></span><font color="#006600"> </font><font color="#0000FF">private static</font> Vector sources<font color="#006600"> = <font color="#0000FF">new</font> </font>Vector();<font color="#006600"> <span class=codeComment>// Holds all validated sources.</span></font> </pre> -<p>Take a close look at the functions and try to understand what we are going - to be doing. Basically what we are trying to create is a system in which we - no longer have to worry about the relationship between buffers and sources. - We can call for the creation of a source from a file and this system will handle - the buffer's creation on it's own so we don't duplicate a buffer (have two buffers - with the same data). This system will handle the buffers as a limited resource, - and will handle that resource efficiently.</p> +<p align="justify">Take a close look at the functions and try to understand what + we are going to be doing. Basically what we are trying to create is a system + in which we no longer have to worry about the relationship between buffers and + sources. We can call for the creation of a source from a file and this system + will handle the buffer's creation on it's own so we don't duplicate a buffer + (have two buffers with the same data). This system will handle the buffers as + a limited resource, and will handle that resource efficiently.</p> <pre class=code><font color="#0000FF">public</font> String getALErrorString(<font color="#0000FF">int</font> err) { <span class=codeKeyword><font color="#0000FF">switch</font></span>(err) { <span class=codeKeyword><font color="#0000FF">case</font></span> AL.AL_NO_ERROR: <span class=codeKeyword><font color="#0000FF">return</font></span> "AL_NO_ERROR"; @@ -119,11 +120,11 @@ public static int </font>loadALBuffer(String path) <font color="#0000FF">throws< } </pre> -<p>This function will convert an OpenAL error code to a string so it can be read - on the console (or some other device). The OpenAL sdk says that the only exception - that needs be looked for in the current version is the 'AL_OUT_OF_MEMORY' error. - However, we will account for all the errors so that our code will be up to date - with later versions.</p> +<p align="justify">This function will convert an OpenAL error code to a string + so it can be read on the console (or some other device). The OpenAL sdk says + that the only exception that needs be looked for in the current version is the + 'AL_OUT_OF_MEMORY' error. However, we will account for all the errors so that + our code will be up to date with later versions.</p> <pre class=code><font color="#0000FF">public</font> String getALCErrorString(<font color="#0000FF">int</font> err) { <span class=codeKeyword><font color="#0000FF">switch</font></span>(err) { <span class=codeKeyword><font color="#0000FF">case</font></span> ALC_NO_ERROR: <span class=codeKeyword><font color="#0000FF">return</font></span> "ALC_NO_ERROR"; @@ -137,14 +138,15 @@ public static int </font>loadALBuffer(String path) <font color="#0000FF">throws< } </pre> -<p>This function will perform a similar task as the previous one accept this one - will interpret Alc errors. OpenAL and Alc share common id's, but not common - enough and not dissimilar enough to use the same function for both.</p> -<p>One more note about the function 'alGetError': The OpenAL sdk defines that - it only holds a single error at a time (i.e. there is no stacking). When the - function is invoked it will return the first error that it has received, and - then clear the error bit to 'AL_NO_ERROR'. In other words an error will only - be stored in the error bit if no previous error is already stored there.</p> +<p align="justify">This function will perform a similar task as the previous one + accept this one will interpret Alc errors. OpenAL and Alc share common id's, + but not common enough and not dissimilar enough to use the same function for + both.</p> +<p align="justify">One more note about the function 'alGetError': The OpenAL sdk + defines that it only holds a single error at a time (i.e. there is no stacking). + When the function is invoked it will return the first error that it has received, + and then clear the error bit to 'AL_NO_ERROR'. In other words an error will + only be stored in the error bit if no previous error is already stored there.</p> <pre class=code><font color="#0000FF">public int</font> loadALBuffer(String path) <font color="#0000FF">throws</font> IOException { <span class=codeComment><font color="#006600">// Variables to store data which defines the buffer.</font></span> <font color="#0000FF">int</font>[] format = <font color="#0000FF">new int</font>[1]; @@ -187,11 +189,12 @@ public static int </font>loadALBuffer(String path) <font color="#0000FF">throws< </font> <span class=codeKeyword><font color="#0000FF">return</font></span> buffer[0]; } </pre> -<p>As you can see we do an error check at every possible phase of the load. Any - number of things can happen at this point which will cause an error to be thrown. - There could be no more system memory either for the buffer creation or the data - to be loaded, the wav file itself may not even exist, or an invalid value can - be passed to any one of the OpenAL functions which will generate an error.</p> +<p align="justify">As you can see we do an error check at every possible phase + of the load. Any number of things can happen at this point which will cause + an error to be thrown. There could be no more system memory either for the buffer + creation or the data to be loaded, the wav file itself may not even exist, or + an invalid value can be passed to any one of the OpenAL functions which will + generate an error.</p> <pre class=code><font color="#0000FF">public int </font>getLoadedALBuffer(String path) <font color="0000ff">throws</font> IOException { <span class=codeKeyword><font color="#0000FF">int</font></span> count = 0; <span class=codeComment><font color="#006600">// 'count' will be an index to the buffer list.</font></span> @@ -220,16 +223,16 @@ public static int </font>loadALBuffer(String path) <font color="#0000FF">throws< } </pre> -<p>This will probably be the piece of code most people have trouble with, but - it's really not that complex. We are doing a search through a list which contains - the file paths of all the wav's we have loaded so far. If one of the paths matches - the one we want to load, we will simply return the id to the buffer we loaded - it into the first time. This way as long as we consistently load our files through - this function, we will never have buffers wasted due to duplication. Every file - loaded this way must also be kept track of with it's own list. The 'buffers' - list is parallel to the 'loadedFiles' list. What I mean by this is that every - buffer in the index of 'buffers', is the same path of the index in 'loadedFiles' - from which that buffer was created.</p> +<p align="justify">This will probably be the piece of code most people have trouble + with, but it's really not that complex. We are doing a search through a list + which contains the file paths of all the wav's we have loaded so far. If one + of the paths matches the one we want to load, we will simply return the id to + the buffer we loaded it into the first time. This way as long as we consistently + load our files through this function, we will never have buffers wasted due + to duplication. Every file loaded this way must also be kept track of with it's + own list. The 'buffers' list is parallel to the 'loadedFiles' list. What I mean + by this is that every buffer in the index of 'buffers', is the same path of + the index in 'loadedFiles' from which that buffer was created.</p> <pre class=code><font color="#0000FF">public static int </font>loadALSample(String path, <span class=codeKeyword><font color="#0000FF">boolean</font></span> loop) <font color="0000ff">throws</font> IOException { <font color="#0000FF">int</font>[] source = <font color="0000ff">new int</font>[1]; <font color="0000ff">int</font> buffer; @@ -260,11 +263,11 @@ public static int </font>loadALBuffer(String path) <font color="#0000FF">throws< <span class=codeKeyword><font color="0000ff">return</font></span> source[0]; } </pre> -<p>Now that we have created a system which will handle the buffers for us, we - just need an extension to it that will get the sources. In this code we obtain - the result of a search for the file, which is the buffer id that the file was - loaded into. This buffer is bound to the new source. We save the source id internally - and also return it.</p> +<p align="justify">Now that we have created a system which will handle the buffers + for us, we just need an extension to it that will get the sources. In this code + we obtain the result of a search for the file, which is the buffer id that the + file was loaded into. This buffer is bound to the new source. We save the source + id internally and also return it.</p> <pre class=code><span class=codeKeyword><font color="#0000FF">public static void</font></span><font color="#0000FF"> </font>killALLoadedData() { loadedFiles.clear(); } @@ -287,13 +290,13 @@ public static int </font>loadALBuffer(String path) <font color="#0000FF">throws< } </pre> -<p>We have seen the function in previous tutorials. It will represent the part - of a program which loads all wav's used by the program. In it we can see why - our system is useful. Even though we have made a call to load the same wav file - into two distinct sources, the buffer for the file 'phaser.wav' will only be - created once, and the sources 'gPhaser1' and 'gPhaser2' will both use that buffer - for playback. There is no more concern for handling buffers because the system - will handle them automatically.</p> +<p align="justify">We have seen the function in previous tutorials. It will represent + the part of a program which loads all wav's used by the program. In it we can + see why our system is useful. Even though we have made a call to load the same + wav file into two distinct sources, the buffer for the file 'phaser.wav' will + only be created once, and the sources 'gPhaser1' and 'gPhaser2' will both use + that buffer for playback. There is no more concern for handling buffers because + the system will handle them automatically.</p> <pre class=code><span class=codeKeyword><font color="#0000FF">public static void</font></span><font color="#0000FF"> </font>killALData() { <font color="006600"> <span class=codeComment>// Release all buffer data.</span> @@ -311,10 +314,10 @@ public static int </font>loadALBuffer(String path) <font color="#0000FF">throws< sources.clear(); } </pre> -<p>All along we have been storing the buffer and source id's into stl vectors. - We free all the buffers and sources by going through them and releasing them - individually. After which we destroy the lists themselves. All we need to do - now is catch the OpenAL errors that we have thrown.</p> +<p align="justify">All along we have been storing the buffer and source id's into + stl vectors. We free all the buffers and sources by going through them and releasing + them individually. After which we destroy the lists themselves. All we need + to do now is catch the OpenAL errors that we have thrown.</p> <pre class=code> <span class=codeKeyword><font color="#0000FF">try</font></span> { initOpenAL(); loadALData(); @@ -323,14 +326,14 @@ public static int </font>loadALBuffer(String path) <font color="#0000FF">throws< } </pre> -<p>If something has gone wrong during the course of the load we will be notified - of it right away. When we catch the error it will be reported on the console. - We can use this for debugging or general error reporting. </p> -<p>That's it. A more advanced way of reporting errors, and a more robust way of - loading your wav files. We may find we need to do some modifications in the - future to allow for more flexibility, but for now we will be using this source - for basic file loading in future tutorials. Expect future tutorials to expand - on this code.</p> +<p align="justify">If something has gone wrong during the course of the load we + will be notified of it right away. When we catch the error it will be reported + on the console. We can use this for debugging or general error reporting. </p> +<p align="justify">That's it. A more advanced way of reporting errors, and a more + robust way of loading your wav files. We may find we need to do some modifications + in the future to allow for more flexibility, but for now we will be using this + source for basic file loading in future tutorials. Expect future tutorials to + expand on this code.</p> <table border="0" cellspacing="1" style="border-collapse: collapse" width="100%" id="AutoNumber2" bgcolor="#666699"> <tr> <td width="40%"> <p dir="ltr"><font color="#FFFFFF" size="2">� 2003 DevMaster.net. |