DecodeSignal: Reset and re-use existing decoder sessions

Instead of destroying and re-creating decoder sessions, re-use
previously created sessions by just terminating their current work and
resetting internal state.

This implementation most proboably is incomplete in respect of changes
to the stack hierarchy or individual decoders' properties. This needs
more attention. When the stack is kept but its configuration has changed,
the involved properties need to get "somehow applied to" the stack's
instances before re-using it with new input data will yield correct results.

diff --git a/pv/data/decodesignal.cpp b/pv/data/decodesignal.cpp
index 77b2061c6e3b793d554613158761d7707a7af127..df385be8d99ce397ed9aba327247f37e0176983b 100644 (file)
--- a/pv/data/decodesignal.cpp
+++ b/pv/data/decodesignal.cpp
@@ -129,6 +129,8 @@ bool DecodeSignal::toggle_decoder_visibility(int index)
 
 void DecodeSignal::reset_decode()
 {
+       terminate_srd_session();
+
        if (decode_thread_.joinable()) {
                decode_interrupt_ = true;
                decode_input_cond_.notify_one();
@@ -157,6 +159,8 @@ void DecodeSignal::reset_decode()
 
 void DecodeSignal::begin_decode()
 {
+       terminate_srd_session();
+
        if (decode_thread_.joinable()) {
                decode_interrupt_ = true;
                decode_input_cond_.notify_one();
@@ -974,14 +978,34 @@ void DecodeSignal::decode_proc()
                        }
                }
        } while (error_message_.isEmpty() && !decode_interrupt_);
+
+       // Potentially reap decoders when the application no longer is
+       // interested in their (pending) results.
+       if (decode_interrupt_)
+               terminate_srd_session();
 }
 
 void DecodeSignal::start_srd_session()
 {
        uint64_t samplerate;
 
-       if (srd_session_)
-               stop_srd_session();
+       if (srd_session_) {
+               // When a decoder stack was created before, re-use it
+               // for the next stream of input data, after terminating
+               // potentially still executing operations, and resetting
+               // internal state. Skip the rather expensive (teardown
+               // and) construction of another decoder stack.
+
+               // TODO Reduce redundancy, use a common code path for
+               // the meta/cb/start sequence?
+               terminate_srd_session();
+               srd_session_metadata_set(srd_session_, SRD_CONF_SAMPLERATE,
+                       g_variant_new_uint64(segments_.at(current_segment_id_).samplerate));
+               srd_pd_output_callback_add(srd_session_, SRD_OUTPUT_ANN,
+                       DecodeSignal::annotation_callback, this);
+               srd_session_start(srd_session_);
+               return;
+       }
 
        // Create the session
        srd_session_new(&srd_session_);
@@ -1017,6 +1041,17 @@ void DecodeSignal::start_srd_session()
        srd_session_start(srd_session_);
 }
 
+void DecodeSignal::terminate_srd_session()
+{
+       // Call the "terminate and reset" routine for the decoder stack
+       // (if available). This does not harm those stacks which already
+       // have completed their operation, and reduces response time for
+       // those stacks which still are processing data while the
+       // application no longer wants them to.
+       if (srd_session_)
+               srd_session_terminate_reset(srd_session_);
+}
+
 void DecodeSignal::stop_srd_session()
 {
        if (srd_session_) {

diff --git a/pv/data/decodesignal.hpp b/pv/data/decodesignal.hpp
index b4f9a2cb0eb3da2795a6299879466c01ac91a724..4f2253d1716091e8a231a8be702a9d5cf0c79cec 100644 (file)
--- a/pv/data/decodesignal.hpp
+++ b/pv/data/decodesignal.hpp
@@ -155,6 +155,7 @@ private:
        void decode_proc();
 
        void start_srd_session();
+       void terminate_srd_session();
        void stop_srd_session();
 
        void connect_input_notifiers();