ima__adpcm_8cpp-source.html

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<a name="l00125"></a><a class="code" href="classIMA__ADPCM.html#a2">00125</a> <a class="code" href="common_8h.html#a2">EXPORT</a> <span class="keywordtype">int</span> <a class="code" href="classIMA__ADPCM.html#a2">IMA_ADPCM::Decode</a>(<a class="code" href="group__integers.html#ga6">uint</a> adpcm)
<a name="l00126"></a>00126     {
<a name="l00127"></a>00127     <span class="keywordtype">int</span> stepIndex = <a class="code" href="classIMA__ADPCM.html#o1">StepIndex</a>;
<a name="l00128"></a>00128     <span class="keywordtype">int</span> step = <a class="code" href="IMA__ADPCM_8cpp.html#a0">IMA_ADPCMStepTable</a>[stepIndex];
<a name="l00129"></a>00129 
<a name="l00130"></a>00130     stepIndex += <a class="code" href="IMA__ADPCM_8cpp.html#a1">IMA_ADPCMIndexTable</a>[adpcm&amp;7];
<a name="l00131"></a>00131     <span class="keywordflow">if</span>(stepIndex&lt;0)
<a name="l00132"></a>00132         stepIndex = 0;
<a name="l00133"></a>00133     <span class="keywordflow">else</span> <span class="keywordflow">if</span>(stepIndex&gt;88)
<a name="l00134"></a>00134         stepIndex = 88;
<a name="l00135"></a>00135     <a class="code" href="classIMA__ADPCM.html#o1">StepIndex</a> = stepIndex;
<a name="l00136"></a>00136 
<a name="l00137"></a>00137     <span class="keywordtype">int</span> diff = step&gt;&gt;3;
<a name="l00138"></a>00138     <span class="keywordflow">if</span>(adpcm&amp;4)
<a name="l00139"></a>00139         diff += step;
<a name="l00140"></a>00140     <span class="keywordflow">if</span>(adpcm&amp;2)
<a name="l00141"></a>00141         diff += step&gt;&gt;1;
<a name="l00142"></a>00142     <span class="keywordflow">if</span>(adpcm&amp;1)
<a name="l00143"></a>00143         diff += step&gt;&gt;2;
<a name="l00144"></a>00144 
<a name="l00145"></a>00145     <span class="keywordtype">int</span> predicedValue = <a class="code" href="classIMA__ADPCM.html#o0">PredictedValue</a>;
<a name="l00146"></a>00146     <span class="keywordflow">if</span>(adpcm&amp;8)
<a name="l00147"></a>00147         predicedValue -= diff;
<a name="l00148"></a>00148     <span class="keywordflow">else</span>
<a name="l00149"></a>00149         predicedValue += diff;
<a name="l00150"></a>00150     <span class="keywordflow">if</span>(predicedValue&lt;-0x8000)
<a name="l00151"></a>00151         predicedValue = -0x8000;
<a name="l00152"></a>00152     <span class="keywordflow">else</span> <span class="keywordflow">if</span>(predicedValue&gt;0x7fff)
<a name="l00153"></a>00153         predicedValue = 0x7fff;
<a name="l00154"></a>00154     <a class="code" href="classIMA__ADPCM.html#o0">PredictedValue</a> = predicedValue;
<a name="l00155"></a>00155 
<a name="l00156"></a>00156     <span class="keywordflow">return</span> predicedValue;
<a name="l00157"></a>00157     }
<a name="l00158"></a>00158 
<a name="l00159"></a>00159 
<a name="l00160"></a><a class="code" href="classIMA__ADPCM.html#a3">00160</a> <a class="code" href="common_8h.html#a2">EXPORT</a> <a class="code" href="group__integers.html#ga6">uint</a> <a class="code" href="classIMA__ADPCM.html#a1">IMA_ADPCM::Encode</a>(<a class="code" href="group__integers.html#ga0">uint8</a>* dst, <span class="keywordtype">int</span> dstOffset, <span class="keyword">const</span> <a class="code" href="group__integers.html#ga4">int16</a>* src, <a class="code" href="group__integers.html#ga6">uint</a> srcSize)
<a name="l00161"></a>00161     {
<a name="l00162"></a>00162     <span class="comment">// use given bit offset</span>
<a name="l00163"></a>00163     dst += dstOffset&gt;&gt;3;
<a name="l00164"></a>00164     <a class="code" href="group__integers.html#ga6">uint</a> bitOffset = dstOffset&amp;4;
<a name="l00165"></a>00165 
<a name="l00166"></a>00166     <span class="comment">// make sure srcSize represents a whole number of samples</span>
<a name="l00167"></a>00167     srcSize &amp;= ~1;
<a name="l00168"></a>00168 
<a name="l00169"></a>00169     <span class="comment">// calculate end of input buffer</span>
<a name="l00170"></a>00170     <span class="keyword">const</span> <a class="code" href="group__integers.html#ga4">int16</a>* end = (<span class="keyword">const</span> <a class="code" href="group__integers.html#ga4">int16</a>*)((<span class="keyword">const</span> <a class="code" href="group__integers.html#ga0">uint8</a>*)src+srcSize);
<a name="l00171"></a>00171 
<a name="l00172"></a>00172     <span class="keywordflow">while</span>(src&lt;end)
<a name="l00173"></a>00173         {
<a name="l00174"></a>00174         <span class="comment">// encode a pcm value from input buffer</span>
<a name="l00175"></a>00175         <a class="code" href="group__integers.html#ga6">uint</a> adpcm = <a class="code" href="classIMA__ADPCM.html#a1">Encode</a>(*src++);
<a name="l00176"></a>00176 
<a name="l00177"></a>00177         <span class="comment">// pick which nibble to write adpcm value to...</span>
<a name="l00178"></a>00178         <span class="keywordflow">if</span>(!bitOffset)
<a name="l00179"></a>00179             *dst = adpcm;       <span class="comment">// write adpcm value to low nibble</span>
<a name="l00180"></a>00180         <span class="keywordflow">else</span>
<a name="l00181"></a>00181             {
<a name="l00182"></a>00182             <a class="code" href="group__integers.html#ga6">uint</a> b = *dst;      <span class="comment">// get byte from ouput</span>
<a name="l00183"></a>00183             b &amp;= 0x0f;          <span class="comment">// clear bits of high nibble</span>
<a name="l00184"></a>00184             b |= adpcm&lt;&lt;4;      <span class="comment">// or adpcm value into the high nibble</span>
<a name="l00185"></a>00185             *dst++ = (<a class="code" href="group__integers.html#ga0">uint8</a>)b;  <span class="comment">// write value back to output and move on to next byte</span>
<a name="l00186"></a>00186             }
<a name="l00187"></a>00187 
<a name="l00188"></a>00188         <span class="comment">// toggle which nibble in byte to write to next</span>
<a name="l00189"></a>00189         bitOffset ^= 4;         
<a name="l00190"></a>00190         }
<a name="l00191"></a>00191 
<a name="l00192"></a>00192     <span class="comment">// return number bits written to dst</span>
<a name="l00193"></a>00193     <span class="keywordflow">return</span> srcSize*2;
<a name="l00194"></a>00194     }
<a name="l00195"></a>00195 
<a name="l00196"></a>00196 
<a name="l00197"></a><a class="code" href="classIMA__ADPCM.html#a4">00197</a> <a class="code" href="common_8h.html#a2">EXPORT</a> <a class="code" href="group__integers.html#ga6">uint</a> <a class="code" href="classIMA__ADPCM.html#a2">IMA_ADPCM::Decode</a>(<a class="code" href="group__integers.html#ga4">int16</a>* dst, <span class="keyword">const</span> <a class="code" href="group__integers.html#ga0">uint8</a>* src, <span class="keywordtype">int</span> srcOffset, <a class="code" href="group__integers.html#ga6">uint</a> srcSize)
<a name="l00198"></a>00198     {
<a name="l00199"></a>00199     <span class="comment">// use given bit offset</span>
<a name="l00200"></a>00200     src += srcOffset&gt;&gt;3;
<a name="l00201"></a>00201 
<a name="l00202"></a>00202     <span class="comment">// calculate pointers to iterate output buffer</span>
<a name="l00203"></a>00203     <a class="code" href="group__integers.html#ga4">int16</a>* out = dst;
<a name="l00204"></a>00204     <a class="code" href="group__integers.html#ga4">int16</a>* end = out+(srcSize&gt;&gt;2);
<a name="l00205"></a>00205 
<a name="l00206"></a>00206     <span class="keywordflow">while</span>(out&lt;end)
<a name="l00207"></a>00207         {
<a name="l00208"></a>00208         <span class="comment">// get byte from src</span>
<a name="l00209"></a>00209         <a class="code" href="group__integers.html#ga6">uint</a> adpcm = *src; 
<a name="l00210"></a>00210 
<a name="l00211"></a>00211         <span class="comment">// pick which nibble holds a adpcm value...</span>
<a name="l00212"></a>00212         <span class="keywordflow">if</span>(srcOffset&amp;4)
<a name="l00213"></a>00213             {
<a name="l00214"></a>00214             adpcm &gt;&gt;= 4;  <span class="comment">// use high nibble of byte</span>
<a name="l00215"></a>00215             ++src;        <span class="comment">// move on a byte for next sample</span>
<a name="l00216"></a>00216             }
<a name="l00217"></a>00217 
<a name="l00218"></a>00218         *out++ = <a class="code" href="classIMA__ADPCM.html#a2">Decode</a>(adpcm);  <span class="comment">// decode value and store it</span>
<a name="l00219"></a>00219 
<a name="l00220"></a>00220         <span class="comment">// toggle which nibble in byte to write to next</span>
<a name="l00221"></a>00221         srcOffset ^= 4;
<a name="l00222"></a>00222         }
<a name="l00223"></a>00223 
<a name="l00224"></a>00224     <span class="comment">// return number of bytes written to dst</span>
<a name="l00225"></a>00225     <span class="keywordflow">return</span> (<a class="code" href="group__integers.html#ga6">uint</a>)out-(<a class="code" href="group__integers.html#ga6">uint</a>)dst;
<a name="l00226"></a>00226     }
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