alternative filter interface (#129)

Add `void FilterGraph::parse(const std::string &graphDescription, OptionalErrorCode ec)`  to allow use FFmpeg-like string description for filter.

Look into example/api2-samples/api2-decode-overlay-encode.cpp for details.

example/api2-samples/api2-decode-overlay-encode.cpp

@@ -0,0 +1,389 @@
+#include <functional>
+#include <iostream>
+#include <map>
+#include <memory>
+#include <set>
+
+#include "audioresampler.h"
+#include "av.h"
+#include "avutils.h"
+#include "codec.h"
+#include "ffmpeg.h"
+#include "packet.h"
+#include "videorescaler.h"
+
+// API2
+#include "codec.h"
+#include "codeccontext.h"
+#include "filters/buffersink.h"
+#include "filters/buffersrc.h"
+#include "filters/filtergraph.h"
+#include "format.h"
+#include "formatcontext.h"
+
+using namespace std;
+using namespace av;
+
+int main(int argc, char **argv)
+{
+    if (argc < 3)
+        return 1;
+
+    av::init();
+    av::setFFmpegLoggingLevel(AV_LOG_DEBUG);
+
+    string uri{argv[1]};
+    string image{argv[2]};
+    string out{argv[3]};
+
+    error_code ec;
+
+    //
+    // INPUT
+    //
+    FormatContext ictx;
+    ssize_t videoStream = -1;
+    VideoDecoderContext vdec;
+    Stream vst;
+
+    int count = 0;
+
+    ictx.openInput(uri, ec);
+    if (ec)
+    {
+        cerr << "Can't open input\n";
+        return 1;
+    }
+
+    ictx.findStreamInfo();
+
+    for (size_t i = 0; i < ictx.streamsCount(); ++i)
+    {
+        auto st = ictx.stream(i);
+        if (st.mediaType() == AVMEDIA_TYPE_VIDEO)
+        {
+            videoStream = i;
+            vst = st;
+            break;
+        }
+    }
+
+    if (vst.isNull())
+    {
+        cerr << "Video stream not found\n";
+        return 1;
+    }
+
+    if (vst.isValid())
+    {
+        vdec = VideoDecoderContext(vst);
+        vdec.setRefCountedFrames(true);
+
+        vdec.open(Codec(), ec);
+        if (ec)
+        {
+            cerr << "Can't open codec\n";
+            return 1;
+        }
+    }
+
+    //
+    // STATIC IMAGE (more or less identical to INPUT)
+    //
+    FormatContext static_image_ctx;
+    ssize_t imageStream = -1;
+    VideoDecoderContext static_image_dec;
+    Stream image_st;
+
+    static_image_ctx.openInput(image, ec);
+    if (ec)
+    {
+        cerr << "Can't open static image\n";
+        return 1;
+    }
+
+    static_image_ctx.findStreamInfo();
+
+    for (size_t i = 0; i < static_image_ctx.streamsCount(); ++i)
+    {
+        auto st = static_image_ctx.stream(i);
+        // An image is still a video stream in the ffmpeg world
+        if (st.mediaType() == AVMEDIA_TYPE_VIDEO)
+        {
+            imageStream = i;
+            image_st = st;
+            break;
+        }
+    }
+
+    if (image_st.isNull())
+    {
+        cerr << "Image stream not found\n";
+        return 1;
+    }
+
+    if (image_st.isValid())
+    {
+        static_image_dec = VideoDecoderContext(image_st);
+        static_image_dec.setRefCountedFrames(true);
+
+        static_image_dec.open(Codec(), ec);
+        if (ec)
+        {
+            cerr << "Can't open codec\n";
+            return 1;
+        }
+    }
+
+    //
+    // OUTPUT
+    //
+    OutputFormat ofrmt;
+    FormatContext octx;
+
+    ofrmt.setFormat(string(), out);
+    octx.setFormat(ofrmt);
+
+    Codec ocodec = findEncodingCodec(ofrmt);
+    VideoEncoderContext encoder{ocodec};
+
+    // Settings
+    encoder.setWidth(vdec.width());
+    encoder.setHeight(vdec.height());
+    if (vdec.pixelFormat() > -1)
+        encoder.setPixelFormat(vdec.pixelFormat());
+    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();
+
+    // FILTER (OVERLAY)
+    FilterGraph filter_graph;
+
+    // Construct the filter descriptor
+    stringstream filter_desc;
+
+    // * for the video input
+    filter_desc << "buffer@in=video_size=" << vdec.width() << "x" << vdec.height() << ":pix_fmt=" << vdec.pixelFormat()
+                << ":time_base=" << encoder.timeBase() << ":pixel_aspect=" << vdec.sampleAspectRatio() << " [in];  ";
+    // * for the fixed image input
+    filter_desc << "buffer@image=video_size=" << static_image_dec.width() << "x" << static_image_dec.height()
+                << ":pix_fmt=" << static_image_dec.pixelFormat() << ":time_base=" << encoder.timeBase()
+                << ":pixel_aspect=" << static_image_dec.sampleAspectRatio() << " [image_unscaled];  ";
+    filter_desc << "[image_unscaled] scale=" << vdec.width() / 4 << "x" << vdec.height() / 4 << " [image];  ";
+    // * for the output
+    filter_desc << "[in][image] overlay=x=50:y=50:repeatlast=1 [out];  ";
+    filter_desc << "[out] buffersink@out";
+
+    // Setup the filter chain
+    clog << "Filter descriptor: " << filter_desc.str() << endl;
+    filter_graph.parse(filter_desc.str(), ec);
+    if (ec)
+    {
+        clog << "Error parsing filter chain: " << ec << ", " << ec.message() << endl;
+        return 1;
+    }
+    filter_graph.config(ec);
+    if (ec)
+    {
+        clog << "Error configuring filter chain: " << ec << ", " << ec.message() << endl;
+        return 1;
+    }
+
+    // Setup the entry/exit points
+    BufferSrcFilterContext buffer_video_src{filter_graph.filter("buffer@in")};
+    BufferSrcFilterContext buffer_image_src{filter_graph.filter("buffer@image")};
+    BufferSinkFilterContext buffer_sink{filter_graph.filter("buffersink@out")};
+
+    // Load the static image into buffer_image_src, it won't change
+    {
+        auto image_pkt = static_image_ctx.readPacket(ec);
+        if (ec)
+        {
+            clog << "Image reading error: " << ec << ", " << ec.message() << endl;
+            return 1;
+        }
+        auto image_frame = static_image_dec.decode(image_pkt, ec);
+        if (ec)
+        {
+            clog << "Image decoding error: " << ec << ", " << ec.message() << endl;
+            return 1;
+        }
+        image_frame.setTimeBase(encoder.timeBase());
+        image_frame.setStreamIndex(0);
+        image_frame.setPictureType();
+        clog << "Frame for overlaying: pts=" << image_frame.pts() << " / " << image_frame.pts().seconds() << " / "
+             << image_frame.timeBase() << ", " << image_frame.width() << "x" << image_frame.height()
+             << ", size=" << image_frame.size() << ", ref=" << image_frame.isReferenced() << ":"
+             << image_frame.refCount() << " / type: " << image_frame.pictureType() << endl;
+        buffer_image_src.addVideoFrame(image_frame, ec);
+        if (ec)
+        {
+            clog << "Image processing error: " << ec << ", " << ec.message() << endl;
+            return 1;
+        }
+        // Very important! Signal that there are no more frames after this one!
+        // ffmpeg expects a full video, this will allow the repeatlast=1 in
+        // overlay to kick in
+        buffer_image_src.writeVideoFrame(VideoFrame::null());
+    }
+
+    //
+    // PROCESS
+    //
+    while (true)
+    {
+
+        // READING
+        Packet pkt = ictx.readPacket(ec);
+        if (ec)
+        {
+            clog << "Packet reading error: " << ec << ", " << ec.message() << endl;
+            break;
+        }
+
+        bool flushDecoder = false;
+        // !EOF
+        if (pkt)
+        {
+            if (pkt.streamIndex() != videoStream)
+            {
+                continue;
+            }
+
+            clog << "Read packet: pts=" << pkt.pts() << ", dts=" << pkt.dts() << " / " << pkt.pts().seconds() << " / "
+                 << pkt.timeBase() << " / st: " << pkt.streamIndex() << endl;
+        }
+        else
+        {
+            flushDecoder = true;
+        }
+
+        do
+        {
+            // DECODING
+            auto frame = vdec.decode(pkt, ec);
+
+            count++;
+            // if (count > 200)
+            //     break;
+
+            bool flushEncoder = false;
+
+            if (ec)
+            {
+                cerr << "Decoding error: " << ec << endl;
+                return 1;
+            }
+            else if (!frame)
+            {
+                if (flushDecoder)
+                {
+                    flushEncoder = true;
+                }
+            }
+
+            if (frame)
+            {
+                clog << "Frame from decoder: pts=" << frame.pts() << " / " << frame.pts().seconds() << " / "
+                     << frame.timeBase() << ", " << frame.width() << "x" << frame.height() << ", size=" << frame.size()
+                     << ", ref=" << frame.isReferenced() << ":" << frame.refCount()
+                     << " / type: " << frame.pictureType() << endl;
+
+                frame.setTimeBase(encoder.timeBase());
+                frame.setStreamIndex(0);
+                frame.setPictureType();
+
+                // Push into the filter
+                buffer_video_src.addVideoFrame(frame, ec);
+                if (ec)
+                {
+                    clog << "Filter push error: " << ec << ", " << ec.message() << endl;
+                    return 1;
+                }
+            }
+
+            // Pull from the filter until there are no more incoming frames
+            VideoFrame filtered;
+            while (buffer_sink.getVideoFrame(filtered, ec))
+            {
+                // Change timebase
+                filtered.setTimeBase(encoder.timeBase());
+                filtered.setStreamIndex(0);
+                filtered.setPictureType();
+                clog << "Frame from filter: pts=" << filtered.pts() << " / " << filtered.pts().seconds() << " / "
+                     << filtered.timeBase() << ", " << filtered.width() << "x" << filtered.height()
+                     << ", size=" << filtered.size() << ", ref=" << filtered.isReferenced() << ":"
+                     << filtered.refCount() << " / type: " << filtered.pictureType() << endl;
+
+                if (filtered || flushEncoder)
+                {
+                    do
+                    {
+                        // Encode
+                        Packet opkt = filtered ? encoder.encode(filtered, ec) : encoder.encode(ec);
+                        if (ec)
+                        {
+                            cerr << "Encoding error: " << ec << endl;
+                            return 1;
+                        }
+                        else if (!opkt)
+                        {
+                            // cerr << "Empty packet\n";
+                            // continue;
+                            break;
+                        }
+
+                        // 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;
+                        }
+                    } while (flushEncoder);
+                }
+            }
+            if (ec && ec.value() != -EAGAIN)
+            {
+                cerr << "Error reading frame from the filter chain: " << ec << ", " << ec.message() << endl;
+                return 1;
+            }
+
+            if (flushEncoder)
+                break;
+
+        } while (flushDecoder);
+
+        if (flushDecoder)
+            break;
+    }
+
+    clog << "done" << endl;
+    octx.writeTrailer();
+}