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Merge pull request #409 from TomHarte/BitShader
Switches ZX80/81 video bit unpacking to the GPU.
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commit
28947bb3c4
@ -10,15 +10,29 @@
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using namespace ZX8081;
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namespace {
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/*!
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The number of bytes of PCM data to allocate at once; if/when more are required,
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the class will simply allocate another batch.
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*/
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const std::size_t StandardAllocationSize = 40;
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/// The amount of time a byte takes to output.
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const std::size_t HalfCyclesPerByte = 8;
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}
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Video::Video() :
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crt_(new Outputs::CRT::CRT(207 * 2, 1, Outputs::CRT::DisplayType::PAL50, 1)) {
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// Set a composite sampling function that assumes 8bpp input grayscale.
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// TODO: lessen this to 1bpp.
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// Set a composite sampling function that assumes 1bpp input.
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crt_->set_composite_sampling_function(
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"float composite_sample(usampler2D sampler, vec2 coordinate, vec2 icoordinate, float phase, float amplitude)"
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"{"
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"return float(texture(texID, coordinate).r) / 255.0;"
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"uint texValue = texture(sampler, coordinate).r;"
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"texValue <<= int(icoordinate.x * 8) & 7;"
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"return float(texValue & 128u);"
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"}");
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// Show only the centre 80% of the TV frame.
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@ -45,10 +59,10 @@ void Video::flush(bool next_sync) {
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if(line_data_) {
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// If there is output data queued, output it either if it's being interrupted by
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// sync, or if we're past its end anyway. Otherwise let it be.
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unsigned int data_length = static_cast<unsigned int>(line_data_pointer_ - line_data_);
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unsigned int data_length = static_cast<unsigned int>(line_data_pointer_ - line_data_) * HalfCyclesPerByte;
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if(data_length < cycles_since_update_ || next_sync) {
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unsigned int output_length = std::min(data_length, cycles_since_update_);
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crt_->output_data(output_length, 1);
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crt_->output_data(output_length, HalfCyclesPerByte);
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line_data_pointer_ = line_data_ = nullptr;
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cycles_since_update_ -= output_length;
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} else return;
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@ -79,25 +93,21 @@ void Video::output_byte(uint8_t byte) {
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// Grab a buffer if one isn't already available.
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if(!line_data_) {
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line_data_pointer_ = line_data_ = crt_->allocate_write_area(320);
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line_data_pointer_ = line_data_ = crt_->allocate_write_area(StandardAllocationSize);
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}
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// If a buffer was obtained, serialise the new pixels.
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if(line_data_) {
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// If the buffer is full, output it now and obtain a new one
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if(line_data_pointer_ - line_data_ == 320) {
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crt_->output_data(320, 1);
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cycles_since_update_ -= 320;
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line_data_pointer_ = line_data_ = crt_->allocate_write_area(320);
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if(line_data_pointer_ - line_data_ == StandardAllocationSize) {
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crt_->output_data(StandardAllocationSize, HalfCyclesPerByte);
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cycles_since_update_ -= StandardAllocationSize * HalfCyclesPerByte;
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line_data_pointer_ = line_data_ = crt_->allocate_write_area(StandardAllocationSize);
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if(!line_data_) return;
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}
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uint8_t mask = 0x80;
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for(int c = 0; c < 8; c++) {
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line_data_pointer_[c] = (byte & mask) ? 0xff : 0x00;
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mask >>= 1;
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}
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line_data_pointer_ += 8;
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line_data_pointer_[0] = byte;
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line_data_pointer_ ++;
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}
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}
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