more generic filter example that also encodes the result (#151)

This improved example also encodes the result and handles correctly streams that require the full input before producing any output (palettegen in this case)

It also adds the example to the makefiles

Author: mmomtchev

example/api2-samples/CMakeLists.txt

@@ -19,6 +19,7 @@ set(TARGETS
   api2-decode-audio
   api2-decode-rasample-audio
   api2-decode-encode-audio
+  api2-decode-filter-encode
   api2-dict-basic
   api2-timestamp
   api2-demux-seek

example/api2-samples/api2-decode-filter.cpp renamed to example/api2-samples/api2-decode-filter-encode.cpp

@@ -24,6 +24,9 @@
 using namespace std;
 using namespace av;
 
+// Example that uses a complex filter to produce a good
+// animated GIF from a video
+
 int main(int argc, char **argv)
 {
     if (argc < 2)
@@ -33,6 +36,7 @@ int main(int argc, char **argv)
     av::setFFmpegLoggingLevel(AV_LOG_DEBUG);
 
     string uri{argv[1]};
+    string out{argv[2]};
 
     ssize_t videoStream = -1;
     VideoDecoderContext vdec;
@@ -98,6 +102,45 @@ int main(int argc, char **argv)
             }
         }
 
+        //
+        // OUTPUT
+        //
+        OutputFormat ofrmt;
+        FormatContext octx;
+
+        ofrmt.setFormat(string(), out);
+        octx.setFormat(ofrmt);
+
+        Codec ocodec = findEncodingCodec(ofrmt);
+        cout << "Codec: " << ocodec.name() << endl;
+        VideoEncoderContext encoder {ocodec};
+
+        // Settings
+        encoder.setWidth(320);
+        encoder.setHeight(200);
+        encoder.setPixelFormat(AV_PIX_FMT_PAL8);
+        encoder.setTimeBase(Rational {1, 1000});
+        encoder.setBitRate(vdec.bitRate());
+
+        encoder.open(Codec(), ec);
+        if (ec) {
+            cerr << "Can't opent encodec\n";
+            return 1;
+        }
+
+        Stream ost = octx.addStream(encoder);
+        ost.setFrameRate(vst.frameRate());
+
+        octx.openOutput(out, ec);
+        if (ec) {
+            cerr << "Can't open output\n";
+            return 1;
+        }
+
+        octx.dump();
+        octx.writeHeader();
+        octx.flush();
+
         // Setup filter
         Filter filter_buffer_src{"buffer"};
         Filter filter_buffer_sink{"buffersink"};
@@ -122,9 +165,16 @@ int main(int argc, char **argv)
         }
 
         // Setup the filter chain
-        filter_graph.parse("scale=320x200", src_ctx, sink_ctx, ec);
-        if (ec)
-        {
+        string filterChain;
+        if (argc > 3) {
+            filterChain = argv[3];
+        } else {
+            filterChain = "scale=320x200:-1:flags=lanczos,split [s0][s1]; "
+                "[s0] palettegen [p]; [s1][p] paletteuse[f]; ";
+        }
+        cout << "Filter: " << filterChain << endl;
+        filter_graph.parse(filterChain, src_ctx, sink_ctx, ec);
+        if (ec) {
             clog << "Error parsing filter chain: " << ec << ", " << ec.message() << endl;
             return 1;
         }
@@ -169,7 +219,13 @@ int main(int argc, char **argv)
                 continue;
             }
 
+            frame.setTimeBase(encoder.timeBase());
+            frame.setStreamIndex(0);
+            frame.setPictureType();
+
             // Push into the filter
+            cout << "Pushing frame into filter: " << frame.width() << "x" << frame.height() << ", size=" << frame.size()
+                 << ", ts=" << frame.pts() << ", tb: " << frame.timeBase() << endl;
             buffer_src.addVideoFrame(frame, AV_BUFFERSRC_FLAG_KEEP_REF, ec);
             if (ec)
             {
@@ -181,55 +237,78 @@ int main(int argc, char **argv)
             VideoFrame filtered;
             while (buffer_sink.getVideoFrame(filtered, ec))
             {
-                filtered.setTimeBase(frame.timeBase());
+                filtered.setTimeBase(encoder.timeBase());
                 auto ts = filtered.pts();
 
                 clog << "  filtered: " << filtered.width() << "x" << filtered.height() << ", size=" << filtered.size()
                      << ", ts=" << ts << ", tm: " << ts.seconds() << ", tb: " << filtered.timeBase()
                      << ", ref=" << filtered.isReferenced() << ":" << filtered.refCount() << endl;
+
+                // Encode
+                Packet opkt = filtered ? encoder.encode(filtered, ec) : encoder.encode(ec);
+                if (ec) {
+                    cerr << "Encoding error: " << ec << endl;
+                    return 1;
+                }
+
+                if (opkt) {
+                    // Only one output stream
+                    opkt.setStreamIndex(0);
+
+                    clog << "Write packet: pts=" << opkt.pts() << ", dts=" << opkt.dts() << " / " << opkt.pts().seconds() << " / " << opkt.timeBase() << " / st: " << opkt.streamIndex() << endl;
+
+                    octx.writePacket(opkt, ec);
+                    if (ec) {
+                        cerr << "Error write packet: " << ec << ", " << ec.message() << endl;
+                        return 1;
+                    }
+                }
             }
             if (ec && ec.value() != -EAGAIN)
             {
                 clog << "Filter pull error: " << ec << ", " << ec.message() << endl;
                 return 1;
             }
+            cout << "No more frames available in filter" << endl;
         }
 
-        clog << "Flush frames;\n";
-        while (true)
+        clog << "Flush frames\n";
+        // Push a null frame at then end for filters that
+        // need the full input before generating any output
+        // (animated GIF with a palette is one of them)
+        auto null_frame = VideoFrame::null();
+        buffer_src.addVideoFrame(null_frame, 0, ec);
+        // Pull until there are no more incoming frames
+        VideoFrame filtered;
+        while (buffer_sink.getVideoFrame(filtered, ec))
         {
-            VideoFrame frame = vdec.decode(Packet(), ec);
-            if (ec)
-            {
-                cerr << "Error: " << ec << ", " << ec.message() << endl;
+            filtered.setTimeBase(encoder.timeBase());
+            auto ts = filtered.pts();
+            clog << "  filtered: " << filtered.width() << "x" << filtered.height() << ", size=" << filtered.size()
+                    << ", ts=" << ts << ", tm: " << ts.seconds() << ", tb: " << filtered.timeBase()
+                    << ", ref=" << filtered.isReferenced() << ":" << filtered.refCount() << endl;
+
+            // Encode
+            Packet opkt = filtered ? encoder.encode(filtered, ec) : encoder.encode(ec);
+            if (ec) {
+                cerr << "Encoding error: " << ec << endl;
                 return 1;
             }
-            if (!frame)
-                break;
 
-            // Push into the filter
-            buffer_src.addVideoFrame(frame, ec);
-            if (ec)
-            {
-                clog << "Filter push error: " << ec << ", " << ec.message() << endl;
-                return 1;
-            }
+            if (opkt) {
+                // Only one output stream
+                opkt.setStreamIndex(0);
 
-            // Pull until there are no more incoming frames
-            VideoFrame filtered;
-            while (buffer_sink.getVideoFrame(filtered, ec))
-            {
-                filtered.setTimeBase(frame.timeBase());
-                auto ts = filtered.pts();
-                clog << "  filtered: " << filtered.width() << "x" << filtered.height() << ", size=" << filtered.size()
-                     << ", ts=" << ts << ", tm: " << ts.seconds() << ", tb: " << filtered.timeBase()
-                     << ", ref=" << filtered.isReferenced() << ":" << filtered.refCount() << endl;
-            }
-            if (ec && ec.value() != -EAGAIN)
-            {
-                clog << "Filter pull error: " << ec << ", " << ec.message() << endl;
-                return 1;
+                clog << "Write packet: pts=" << opkt.pts() << ", dts=" << opkt.dts() << " / " << opkt.pts().seconds() << " / " << opkt.timeBase() << " / st: " << opkt.streamIndex() << endl;
+
+                octx.writePacket(opkt, ec);
+                if (ec) {
+                    cerr << "Error write packet: " << ec << ", " << ec.message() << endl;
+                    return 1;
+                }
             }
         }
+        cout << "Filter flushed, frames: " << count << endl;
+        octx.writeTrailer();
     }
 }

example/api2-samples/meson.build

@@ -14,6 +14,7 @@ samples = [
     'api2-decode-audio',
     'api2-decode-rasample-audio',
     'api2-decode-encode-audio',
+    'api2-decode-filter-encode',
     'api2-dict-basic',
     'api2-timestamp',
     'api2-demux-seek',