Add support for the new bcg729 API, introduced in version 1.0.2

Starting with version 1.0.2, bcg729 has changed its API to add support
for G.729B, thus requiring us to adjust our function calls depending on
which version is installed.

When dealing with the new API, we merely need to add a few parameters to
disable all G.729B features, namely:

* On the decoder side: When `SIDFrameFlag` is not set, the decoder will
  behave just like before, decoding the payload as a standard G.729A
  voice frame (or concealing an erased frame).  The other parameters,
  `rfc3389PayloadFlag` and `bitStreamLength`, are only of use when
  dealing with a SID frame sent as per RFC 3389, and are ignored if
  `SIDFrameFlag` is not set.

* On the encoder side: When `enableVAD` is disabled, the encoder will
  behave just like before, producing only standard G.729A voice frames.
  The only API difference is the introduction of `*bitStreamLength`, to
  return the length of the encoded frame (0, 2 or 10 bytes).  In our
  case, this will always be 10 bytes just like before; an assert() was
  added to guarantee this.

Closes #104

5 files changed, 59 insertions, 0 deletions

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 1dafe55..7e3fde0 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -116,6 +116,10 @@ if (WITH_G729)
 	if (G729_FOUND)
 		message(STATUS "bcg729 OK")
 		set(HAVE_BCG729 TRUE)
+
+		if (G729_ANNEX_B)
+			set(HAVE_BCG729_ANNEX_B TRUE)
+		endif (G729_ANNEX_B)
 		
 		include_directories(${G729_INCLUDE_DIR})
 	else (G729_FOUND)
diff --git a/cmake/FindG729.cmake b/cmake/FindG729.cmake
index 4a30ba0..1fbfeeb 100644
--- a/cmake/FindG729.cmake
+++ b/cmake/FindG729.cmake
@@ -1,14 +1,50 @@
+INCLUDE(CMakePushCheckState)
+INCLUDE(CheckCSourceCompiles)
+
 FIND_PATH(G729_INCLUDE_DIR bcg729/decoder.h)
 FIND_LIBRARY(G729_LIBRARY NAMES bcg729)
 
 IF(G729_INCLUDE_DIR AND G729_LIBRARY)
 	SET(G729_FOUND TRUE)
+
+	# The bcg729 API was changed in 1.0.2 to add support for G.729 Annex B.
+	# This checks whether we are dealing with the old or new API.
+	CMAKE_PUSH_CHECK_STATE()
+	SET(CMAKE_REQUIRED_INCLUDES "${INCLUDE_DIRECTORIES}" "${G729_INCLUDE_DIR}")
+	SET(CMAKE_REQUIRED_LIBRARIES "${G729_LIBRARY}")
+	SET(CMAKE_REQUIRED_QUIET TRUE)
+	# Try to compile something using the old (pre-1.0.2) API.
+	#
+	# We cannot do it the other way around, as initBcg729EncoderChannel()
+	# did not have a prototype before 1.0.2, thus compilation would not fail
+	# when passing it an extra argument.
+	CHECK_C_SOURCE_COMPILES("
+		#include <bcg729/encoder.h>
+
+		int main() {
+			/* This function requires an argument since 1.0.2 */
+			initBcg729EncoderChannel();
+			return 0;
+		}
+	" G729_OLD_API)
+	CMAKE_POP_CHECK_STATE()
+
+	IF (G729_OLD_API)
+		SET(G729_ANNEX_B FALSE)
+	ELSE (G729_OLD_API)
+		SET(G729_ANNEX_B TRUE)
+	ENDIF (G729_OLD_API)
 ENDIF(G729_INCLUDE_DIR AND G729_LIBRARY)
 
 IF(G729_FOUND)
 	IF (NOT G729_FIND_QUIETLY)
 		MESSAGE(STATUS "Found bcg729 includes:	${G729_INCLUDE_DIR}/bcg729/decoder.h")
 		MESSAGE(STATUS "Found bcg729 library: ${G729_LIBRARY}")
+		IF (G729_ANNEX_B)
+			MESSAGE(STATUS "bcg729 supports Annex B; using the new (1.0.2) API")
+		ELSE (G729_ANNEX_B)
+			MESSAGE(STATUS "bcg729 does not support Annex B; using the old (pre-1.0.2) API")
+		ENDIF (G729_ANNEX_B)
 	ENDIF (NOT G729_FIND_QUIETLY)
 ELSE(G729_FOUND)
 	IF (G729_FIND_REQUIRED)
diff --git a/src/audio/audio_decoder.cpp b/src/audio/audio_decoder.cpp
index 65935dd..c661910 100644
--- a/src/audio/audio_decoder.cpp
+++ b/src/audio/audio_decoder.cpp
@@ -547,7 +547,11 @@ uint16 t_g729a_audio_decoder::decode(uint8 *payload, uint16 payload_size,
 
 	for (uint16 done = 0; done < payload_size; done += 10)
 	{
+#ifdef HAVE_BCG729_ANNEX_B
+		bcg729Decoder(_context, &payload[done], 0, false, false, false, &pcm_buf[done * 8]);
+#else
 		bcg729Decoder(_context, &payload[done], false, &pcm_buf[done * 8]);
+#endif
 	}
 
 	return payload_size * 8;
@@ -562,7 +566,11 @@ uint16 t_g729a_audio_decoder::conceal(int16 *pcm_buf, uint16 pcm_buf_size)
 {
 	assert(pcm_buf_size >= 80);
 
+#ifdef HAVE_BCG729_ANNEX_B
+	bcg729Decoder(_context, nullptr, 0, true, false, false, pcm_buf);
+#else
 	bcg729Decoder(_context, nullptr, true, pcm_buf);
+#endif
 	return 80;
 }
 
diff --git a/src/audio/audio_encoder.cpp b/src/audio/audio_encoder.cpp
index d6ff356..952b1ee 100644
--- a/src/audio/audio_encoder.cpp
+++ b/src/audio/audio_encoder.cpp
@@ -433,7 +433,11 @@ uint16 t_g726_audio_encoder::encode(int16 *sample_buf, uint16 nsamples,
 t_g729a_audio_encoder::t_g729a_audio_encoder(uint16 payload_id, uint16 ptime, t_user *user_config)
 	: t_audio_encoder(payload_id, ptime, user_config)
 {
+#ifdef HAVE_BCG729_ANNEX_B
+	_context = initBcg729EncoderChannel(false);
+#else
 	_context = initBcg729EncoderChannel();
+#endif
 }
 
 t_g729a_audio_encoder::~t_g729a_audio_encoder()
@@ -451,7 +455,13 @@ uint16 t_g729a_audio_encoder::encode(int16 *sample_buf, uint16 nsamples,
 
 	for (uint16 done = 0; done < nsamples; done += 80)
 	{
+#ifdef HAVE_BCG729_ANNEX_B
+		uint8 frame_size = 10;
+		bcg729Encoder(_context, &sample_buf[done], &payload[done / 8], &frame_size);
+		assert(frame_size == 10);
+#else
 		bcg729Encoder(_context, &sample_buf[done], &payload[done / 8]);
+#endif
 	}
 
 	return nsamples / 8;
diff --git a/twinkle_config.h.in b/twinkle_config.h.in
index a1aa3b4..53a0426 100644
--- a/twinkle_config.h.in
+++ b/twinkle_config.h.in
@@ -4,6 +4,7 @@
 #cmakedefine HAVE_ILBC_CPP
 #cmakedefine HAVE_ZRTP
 #cmakedefine HAVE_BCG729
+#cmakedefine HAVE_BCG729_ANNEX_B
 #cmakedefine HAVE_GSM
 
 #cmakedefine HAVE_UNISTD_H