在iOS 8中的程序员获取HW-H264解码器的通知之后,我想现在使用它.有一个很好的介绍,直接访问视频编码和解码从WWDC 2014年那里.你可以看看
here.
基于案例1,我开始开发一个应用程序,应该可以从GStreamer获取一个H264-RTP-UDP-Stream,将其下载到一个“appsink”元素中,以直接访问NAL单元并执行转换创建CMSampleBuffers,我的AVSampleBufferDisplayLayer可以显示.
有趣的代码如下：
// // GStreamerBackend.m // #import "GStreamerBackend.h" Nsstring * const naluTypesstrings[] = { @"Unspecified (non-VCL)",@"Coded slice of a non-IDR picture (VCL)",@"Coded slice data partition A (VCL)",@"Coded slice data partition B (VCL)",@"Coded slice data partition C (VCL)",@"Coded slice of an IDR picture (VCL)",@"Supplemental enhancement information (SEI) (non-VCL)",@"Sequence parameter set (non-VCL)",@"Picture parameter set (non-VCL)",@"Access unit delimiter (non-VCL)",@"End of sequence (non-VCL)",@"End of stream (non-VCL)",@"Filler data (non-VCL)",@"Sequence parameter set extension (non-VCL)",@"Prefix NAL unit (non-VCL)",@"Subset sequence parameter set (non-VCL)",@"Reserved (non-VCL)",@"Coded slice of an auxiliary coded picture without partitioning (non-VCL)",@"Coded slice extension (non-VCL)",@"Coded slice extension for depth view components (non-VCL)",@"Unspecified (non-VCL)",}; static GstFlowReturn new_sample(GstAppSink *sink,gpointer user_data) { GStreamerBackend *backend = (__bridge GStreamerBackend *)(user_data); GstSample *sample = gst_app_sink_pull_sample(sink); GstBuffer *buffer = gst_sample_get_buffer(sample); GstMemory *memory = gst_buffer_get_all_memory(buffer); GstMapInfo info; gst_memory_map (memory,&info,GST_MAP_READ); int startCodeIndex = 0; for (int i = 0; i < 5; i++) { if (info.data[i] == 0x01) { startCodeIndex = i; break; } } int nalu_type = ((uint8_t)info.data[startCodeIndex + 1] & 0x1F); NSLog(@"NALU with Type \"%@\" received.",naluTypesstrings[nalu_type]); if(backend.searchForSPSAndPPS) { if (nalu_type == 7) backend.spsData = [NSData dataWithBytes:&(info.data[startCodeIndex + 1]) length: info.size - 4]; if (nalu_type == 8) backend.ppsData = [NSData dataWithBytes:&(info.data[startCodeIndex + 1]) length: info.size - 4]; if (backend.spsData != nil && backend.ppsData != nil) { const uint8_t* const parameterSetPointers[2] = { (const uint8_t*)[backend.spsData bytes],(const uint8_t*)[backend.ppsData bytes] }; const size_t parameterSetSizes[2] = { [backend.spsData length],[backend.ppsData length] }; CMVideoFormatDescriptionRef videoFormatDescr; Osstatus status = CMVideoFormatDescriptionCreateFromH264ParameterSets(kcfAllocatorDefault,2,parameterSetPointers,parameterSetSizes,4,&videoFormatDescr); [backend setVideoFormatDescr:videoFormatDescr]; [backend setSearchForSPSAndPPS:false]; NSLog(@"Found all data for CMVideoFormatDescription. Creation: %@.",(status == noErr) ? @"successfully." : @"Failed."); } } if (nalu_type == 1 || nalu_type == 5) { CMBlockBufferRef videoBlock = NULL; Osstatus status = CMBlockBufferCreateWithMemoryBlock(NULL,info.data,info.size,kcfAllocatorNull,NULL,&videoBlock); NSLog(@"BlockBufferCreation: %@",(status == kCMBlockBufferNoErr) ? @"successfully." : @"Failed."); const uint8_t sourceBytes[] = {(uint8_t)(info.size >> 24),(uint8_t)(info.size >> 16),(uint8_t)(info.size >> 8),(uint8_t)info.size}; status = CMBlockBufferReplaceDataBytes(sourceBytes,videoBlock,4); NSLog(@"BlockBufferReplace: %@",(status == kCMBlockBufferNoErr) ? @"successfully." : @"Failed."); CMSampleBufferRef sbRef = NULL; const size_t sampleSizeArray[] = {info.size}; status = CMSampleBufferCreate(kcfAllocatorDefault,true,backend.videoFormatDescr,1,sampleSizeArray,&sbRef); NSLog(@"SampleBufferCreate: %@",(status == noErr) ? @"successfully." : @"Failed."); CFArrayRef attachments = CMSampleBufferGetSampleAttachmentsArray(sbRef,YES); cfmutabledictionaryRef dict = (cfmutabledictionaryRef)CFArrayGetValueAtIndex(attachments,0); CFDictionarySetValue(dict,kCMSampleAttachmentKey_displayImmediately,kcfBooleanTrue); NSLog(@"Error: %@,Status:%@",backend.displayLayer.error,(backend.displayLayer.status == AVQueuedSampleBufferRenderingStatusUnkNown)?@"unkNown":((backend.displayLayer.status == AVQueuedSampleBufferRenderingStatusRendering)?@"rendering":@"Failed")); dispatch_async(dispatch_get_main_queue(),^{ [backend.displayLayer enqueueSampleBuffer:sbRef]; [backend.displayLayer setNeedsdisplay]; }); } gst_memory_unmap(memory,&info); gst_memory_unref(memory); gst_buffer_unref(buffer); return GST_FLOW_OK; } @implementation GStreamerBackend - (instancetype)init { if (self = [super init]) { self.searchForSPSAndPPS = true; self.ppsData = nil; self.spsData = nil; self.displayLayer = [[AVSampleBufferdisplayLayer alloc] init]; self.displayLayer.bounds = CGRectMake(0,300,300); self.displayLayer.backgroundColor = [UIColor blackColor].CGColor; self.displayLayer.position = CGPointMake(500,500); self.queue = dispatch_get_global_queue(disPATCH_QUEUE_PRIORITY_DEFAULT,0); dispatch_async(self.queue,^{ [self app_function]; }); } return self; } - (void)start { if(gst_element_set_state(self.pipeline,GST_STATE_PLAYING) == GST_STATE_CHANGE_FAILURE) { NSLog(@"Failed to set pipeline to playing"); } } - (void)app_function { GstElement *udpsrc,*rtphdepay,*capsfilter; GMainContext *context; /* GLib context used to run the main loop */ GMainLoop *main_loop; /* GLib main loop */ context = g_main_context_new (); g_main_context_push_thread_default(context); g_set_application_name ("appsink"); self.pipeline = gst_pipeline_new ("testpipe"); udpsrc = gst_element_factory_make ("udpsrc","udpsrc"); GstCaps *caps = gst_caps_new_simple("application/x-rtp","media",G_TYPE_STRING,"video","clock-rate",G_TYPE_INT,90000,"encoding-name","H264",NULL); g_object_set(udpsrc,"caps",caps,"port",5000,NULL); gst_caps_unref(caps); rtphdepay = gst_element_factory_make("rtph264depay","rtph264depay"); capsfilter = gst_element_factory_make("capsfilter","capsfilter"); caps = gst_caps_new_simple("video/x-h264","streamformat","byte-stream","alignment","nal",NULL); g_object_set(capsfilter,NULL); self.appsink = gst_element_factory_make ("appsink","appsink"); gst_bin_add_many (GST_BIN (self.pipeline),udpsrc,rtphdepay,capsfilter,self.appsink,NULL); if(!gst_element_link_many (udpsrc,NULL)) { NSLog(@"Cannot link gstreamer elements"); exit (1); } if(gst_element_set_state(self.pipeline,GST_STATE_READY) != GST_STATE_CHANGE_SUCCESS) NSLog(@"Could not change to ready"); GstAppSinkCallbacks callbacks = { NULL,new_sample,NULL}; gst_app_sink_set_callbacks (GST_APP_SINK(self.appsink),&callbacks,(__bridge gpointer)(self),NULL); main_loop = g_main_loop_new (context,FALSE); g_main_loop_run (main_loop); /* Free resources */ g_main_loop_unref (main_loop); main_loop = NULL; g_main_context_pop_thread_default(context); g_main_context_unref (context); gst_element_set_state (GST_ELEMENT (self.pipeline),GST_STATE_NULL); gst_object_unref (GST_OBJECT (self.pipeline)); } @end
运行应用程序并开始流式传输到iOS设备时所获得的内容：
NALU with Type "Sequence parameter set (non-VCL)" received. NALU with Type "Picture parameter set (non-VCL)" received. Found all data for CMVideoFormatDescription. Creation: successfully.. NALU with Type "Coded slice of an IDR picture (VCL)" received. BlockBufferCreation: successfully. BlockBufferReplace: successfully. SampleBufferCreate: successfully. Error: (null),Status:unkNown NALU with Type "Coded slice of a non-IDR picture (VCL)" received. BlockBufferCreation: successfully. BlockBufferReplace: successfully. SampleBufferCreate: successfully. Error: (null),Status:rendering [...] (repetition of the last 5 lines)
所以似乎解码,因为它应该做,但我的问题是,我看不到任何东西在我的AVSampleBufferdisplayLayer.
这可能是kCMSampleAttachmentKey_DisplayImmediately的一个问题,但我已经设置好像我被告知到here (see the ‘important’ note).
欢迎每一个想法;)
解决方法
现在工作了每个NALU的长度不包含长度头本身.所以我已经从我的info.size中减去4,然后再将它用于我的sourceBytes.
