Wraps two av functions in c++

lib/av/av.cpp

@@ -6,9 +6,15 @@ extern "C" {
 #include <libavcodec/avcodec.h>
 }
 
+#include <iostream>
 #include <string>
 #include <cassert>
 
+// Was not yet defined in <string> :(
+static std::string operator "" s(const char *str, std::size_t len){
+	return {str, len};
+}
+
 namespace av {
 
 	format_context format_open_input(const std::string& filename, AVInputFormat* format, AVDictionary** options){
@@ -98,4 +104,23 @@ namespace av {
 		return crop(frame_clone(f), left, top, width, height);
 	}
 
+
+	bool codec_decode_video(codec_context& ctx, frame& f, const packet& pkt){
+		int finished = 0;
+		int ret = avcodec_decode_video2(ctx.get(), f.get(), &finished, pkt.get());
+		if (ret < 0) {
+			throw std::runtime_error("Error ["s + std::to_string(ret) + "] while decoding frame: "s + strerror(AVERROR(ret)));
+		}
+		return finished;
+	}
+
+	void codec_decode_video_remaining(codec_context& ctx, frame& f){
+		AVPacket pkt{0, 0, 0, 0, 0}; // data and size should be 0
+		int finished = 0;
+		int ret = avcodec_decode_video2(ctx.get(), f.get(), &finished, &pkt);
+		if (ret < 0) {
+			throw std::runtime_error("Error ["s + std::to_string(ret) + "] while decoding remaining frame: "s + strerror(AVERROR(ret)));
+		}
+	}
+
 }

lib/av/av.hpp

@@ -45,4 +45,9 @@ namespace av {
 	void crop(frame & f, int left, int top, int width, int height);
 	frame crop(frame && f, int left, int top, int width, int height);
 	frame crop(frame const & f, int left, int top, int width, int height);
+
+
+	//
+	bool codec_decode_video(codec_context & ctx, frame & f, packet const & pkt);
+	void codec_decode_video_remaining(codec_context & ctx, frame & f);
 }

lib/image_io.cpp

@@ -55,23 +55,21 @@ av::frame open_image(std::string const & filename){
 
 	// things to read and decode it
 	av::packet_buffer empty_packet;
-	int finished = 0;
+	bool need_extra_pass = true;
 	while(auto packet = av::read_frame(format_context, empty_packet)) {
 		if(packet->stream_index != 0) continue;
 
-		int ret = avcodec_decode_video2(codec_context.get(), frame.get(), &finished, packet.get());
-		if (ret <= 0) {
-			printf("Error [%d] while decoding frame: %s\n", ret, strerror(AVERROR(ret)));
-			throw std::runtime_error("boem packet");
-		}
-
 		// we only need the first frame
-		if(finished) break;
+		if(av::codec_decode_video(codec_context, frame, packet)) {
+			need_extra_pass = false;
+			break;
+		}
 	}
 
-	// some decoders need extra passes
-	while(!finished) {
-		avcodec_decode_video2(codec_context.get(), frame.get(), &finished, &empty_packet);
+	// some decoders need an extra pass
+	// See the flag CODEC_CAP_DELAY for more info
+	if(need_extra_pass) {
+		av::codec_decode_video_remaining(codec_context, frame);
 	}
 
 	return frame;