Implement code for new video decoder (untested) based on http://stackoverflow.com/questions/25980070/how-to-use-avsamplebufferdisplaylayer-in-ios-8-for-rtp-h264-streams-with-gstream

Limelight/VideoDecoderRenderer.m

@@ -8,20 +8,124 @@
 
 #import "VideoDecoderRenderer.h"
 
-@implementation VideoDecoderRenderer
+@implementation VideoDecoderRenderer {
+    AVSampleBufferDisplayLayer* displayLayer;
+    Boolean waitingForSps, waitingForPpsA, waitingForPpsB;
+    
+    NSData *spsData, *ppsDataA, *ppsDataB;
+    CMVideoFormatDescriptionRef formatDesc;
+}
 
-- (id)initWithTarget:(UIView *)target
+- (id)init
 {
     self = [super init];
     
-    self.renderTarget = target;
+    displayLayer = [[AVSampleBufferDisplayLayer alloc] init];
+    displayLayer.bounds = CGRectMake(0, 0, 300, 300);
+    displayLayer.backgroundColor = [UIColor blackColor].CGColor;
+    displayLayer.position = CGPointMake(500, 500);
+    
+    // We need some parameter sets before we can properly start decoding frames
+    waitingForSps = true;
+    waitingForPpsA = true;
+    waitingForPpsB = true;
     
     return self;
 }
 
-- (void)main
+#define ES_START_PREFIX_SIZE 4
+#define ES_DATA_OFFSET 5
+- (void)submitDecodeBuffer:(unsigned char *)data length:(int)length
 {
-    NSLog(@"Hi");
+    unsigned char nalType = data[ES_START_PREFIX_SIZE] & 0x1F;
+    OSStatus status;
+    
+    if (formatDesc == NULL && (nalType == 0x7 || nalType == 0x8)) {
+        if (waitingForSps && nalType == 0x7) {
+            spsData = [NSData dataWithBytes:&data[ES_DATA_OFFSET] length:length - ES_DATA_OFFSET];
+            waitingForSps = false;
+        }
+        // Nvidia's stream has 2 PPS NALUs so we'll wait for both of them
+        else if ((waitingForPpsA || waitingForPpsB) && nalType == 0x8) {
+            // Read the NALU's PPS index to figure out which PPS this is
+            if (data[ES_DATA_OFFSET] == 0) {
+                if (waitingForPpsA) {
+                    ppsDataA = [NSData dataWithBytes:&data[ES_DATA_OFFSET] length:length - ES_DATA_OFFSET];
+                    waitingForPpsA = false;
+                }
+            }
+            else if (data[ES_DATA_OFFSET] == 1) {
+                if (waitingForPpsB) {
+                    ppsDataA = [NSData dataWithBytes:&data[ES_DATA_OFFSET] length:length - ES_DATA_OFFSET];
+                    waitingForPpsB = false;
+                }
+            }
+        }
+        
+        // See if we've got all the parameter sets we need
+        if (!waitingForSps && !waitingForPpsA && !waitingForPpsB) {
+            const uint8_t* const parameterSetPointers[] = { [spsData bytes], [ppsDataA bytes], [ppsDataB bytes] };
+            const size_t parameterSetSizes[] = { [spsData length], [ppsDataA length], [ppsDataB length] };
+            
+            status = CMVideoFormatDescriptionCreateFromH264ParameterSets(kCFAllocatorDefault,
+                                                                         3, /* count of parameter sets */
+                                                                         parameterSetPointers,
+                                                                         parameterSetSizes,
+                                                                         4 /* size of length prefix */,
+                                                                         &formatDesc);
+            if (status != noErr) {
+                NSLog(@"Failed to create format description: %d", (int)status);
+                formatDesc = NULL;
+                return;
+            }
+        }
+        
+        // No frame data to submit for these NALUs
+        return;
+    }
+    
+    if (formatDesc == NULL) {
+        // Can't decode if we haven't gotten our parameter sets yet
+        return;
+    }
+    
+    // Now we're decoding actual frame data here
+    CMBlockBufferRef blockBuffer;
+    status = CMBlockBufferCreateWithMemoryBlock(NULL, data, length, kCFAllocatorNull, NULL, 0, length, 0, &blockBuffer);
+    if (status != noErr) {
+        NSLog(@"CMBlockBufferCreateWithMemoryBlock failed: %d", (int)status);
+        return;
+    }
+    
+    // Compute the new length prefix to replace the 00 00 00 01
+    const uint8_t lengthBytes[] = {(uint8_t)(length >> 24), (uint8_t)(length >> 16), (uint8_t)(length >> 8), (uint8_t)length};
+    status = CMBlockBufferReplaceDataBytes(lengthBytes, blockBuffer, 0, 4);
+    if (status != noErr) {
+        NSLog(@"CMBlockBufferReplaceDataBytes failed: %d", (int)status);
+        return;
+    }
+    
+    CMSampleBufferRef sampleBuffer;
+    const size_t sampleSizeArray[] = {length};
+    
+    status = CMSampleBufferCreate(kCFAllocatorDefault,
+                                  blockBuffer, true, NULL,
+                                  NULL, formatDesc, 1, 0,
+                                  NULL, 1, sampleSizeArray,
+                                  &sampleBuffer);
+    if (status != noErr) {
+        NSLog(@"CMSampleBufferCreate failed: %d", (int)status);
+        return;
+    }
+    
+    CFArrayRef attachments = CMSampleBufferGetSampleAttachmentsArray(sampleBuffer, YES);
+    CFMutableDictionaryRef dict = (CFMutableDictionaryRef)CFArrayGetValueAtIndex(attachments, 0);
+    CFDictionarySetValue(dict, kCMSampleAttachmentKey_DisplayImmediately, kCFBooleanTrue);
+    
+    dispatch_async(dispatch_get_main_queue(),^{
+        [displayLayer enqueueSampleBuffer:sampleBuffer];
+        [displayLayer setNeedsDisplay];
+    });
 }
 
 @end