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    <p>The data array is not an array of 8 uint_8 but rather an array of 8 <strong>pointers</strong> to uint_8. Note the asterik before the data. - The type is uint8_t* - that is <strong>pointer</strong> to uint8_t.</p> <pre><code>uint8_t *data[AV_NUM_DATA_POINTERS]; </code></pre> <p>In C, an array is similar to a pointer, so if you have a pointer to uint8_t, you can access the addresses it points to, and subsequent addresses, as an array.</p> <p>You do need to have this allocated properly or you will either get a segmentation fault, or some data you don't expect - but this is probably handled properly by your library.</p> <p>C also uses special arithmetic for pointers (pointer arithmetic) - so the type of pointer determines the "spacing" between elements - so if you have a pointer to a uint8_t, array elements will be handled with each element being 1 byte from the previous. If the type is uint32_t, then each element would be 4 bytes from the previous element - to accomodate the larger type.</p> <p>You can find more info on C arrays and pointer arithmetic here:</p> <p><a href="http://www-ee.eng.hawaii.edu/~tep/EE160/Book/chap7/section2.1.3.html" rel="nofollow">C arrays and pointer arithmetic</a></p> <p>So since data[] is an array of pointers to uint8_t, then data[0] is a pointer to uint8_t. Since you can treat this pointer as the start of an array of uint8_t then </p> <p>picture_hq->data[0][y * picture_hq->linesize[0] + x] = native_video_frame_data[0];</p> <p>access the (y * picture_hq->linesize[0] + x) offset from the address pointed to by data[0], and treats it as a uint8_t.</p>
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    1. POC-1 dimension array of uint8_t is actually 2 dimensions array?
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    1. USAvi Perel
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    1. CO"*In C, an array is similar to a pointer*" -- No, it really isn't. And your [linked article](http://www-ee.eng.hawaii.edu/~tep/EE160/Book/chap7/section2.1.3.html) is badly misleading; for example, declaring an array object *does not* allocate a pointer object. Read section 6 of the [comp.lang.c FAQ](http://www.c-faq.com); it explains this stuff clearly *and correctly*.
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      1. USKeith Thompson
    2. CO@Keith Thompson - respectfully, I was not saying that declaring an array allocates a pointer, and also specifically noted that declaring a pointer does not allocates an array - it is the programmers responsibilty to do this (3rd paragraph).
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    3. COThe article you linked to says "Thus, the declaration of an array causes the compiler to allocate the specified number of contiguous cells of the indicated type, as well as to allocate an appropriate pointer cell, initialized to point to the first cell of the array." That was actually true in C as it existed about 40 years ago, but it's simply wrong now. And my main quibble is with your statement that "an array is similar to a pointer". An array is a contiguous sequence of elements; a pointer contains a memory address. They are not similar.
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