input/ffmpeg: use av_strerror()

Generate more detailed error messages.

Makefile.am

@@ -781,6 +781,7 @@ endif
 if HAVE_FFMPEG
 noinst_LIBRARIES += libffmpeg.a
 libffmpeg_a_SOURCES = \
+	src/lib/ffmpeg/Error.cxx src/lib/ffmpeg/Error.hxx \
 	src/lib/ffmpeg/Domain.cxx src/lib/ffmpeg/Domain.hxx
 FFMPEG_LIBS2 = libffmpeg.a $(FFMPEG_LIBS)
 endif

NEWS

@@ -31,6 +31,7 @@ ver 0.19 (not yet released)
   - alsa: new input plugin
   - curl: options "verify_peer" and "verify_host"
   - ffmpeg: update offset after seeking
+  - ffmpeg: improved error messages
   - mms: non-blocking I/O
   - nfs: new input plugin
   - smbclient: new input plugin

src/input/plugins/FfmpegInputPlugin.cxx

@@ -23,6 +23,7 @@
 #include "config.h"
 #include "FfmpegInputPlugin.hxx"
 #include "lib/ffmpeg/Domain.hxx"
+#include "lib/ffmpeg/Error.hxx"
 #include "../InputStream.hxx"
 #include "../InputPlugin.hxx"
 #include "util/StringUtil.hxx"
@@ -101,8 +102,7 @@ input_ffmpeg_open(const char *uri,
 	AVIOContext *h;
 	auto result = avio_open(&h, uri, AVIO_FLAG_READ);
 	if (result != 0) {
-		error.Set(ffmpeg_domain, result,
+		SetFfmpegError(error, result);
-			  "libavformat failed to open the URI");
 		return nullptr;
 	}
 
@@ -115,7 +115,7 @@ FfmpegInputStream::Read(void *ptr, size_t read_size, Error &error)
 	auto result = avio_read(h, (unsigned char *)ptr, read_size);
 	if (result <= 0) {
 		if (result < 0)
-			error.Set(ffmpeg_domain, "avio_read() failed");
+			SetFfmpegError(error, result, "avio_read() failed");
 
 		eof = true;
 		return false;
@@ -137,7 +137,7 @@ FfmpegInputStream::Seek(offset_type new_offset, Error &error)
 	auto result = avio_seek(h, new_offset, SEEK_SET);
 
 	if (result < 0) {
-		error.Set(ffmpeg_domain, "avio_seek() failed");
+		SetFfmpegError(error, result, "avio_seek() failed");
 		return false;
 	}
 

src/lib/ffmpeg/Error.cxx

@@ -0,0 +1,43 @@
+/*
+ * Copyright (C) 2003-2014 The Music Player Daemon Project
+ * http://www.musicpd.org
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#include "config.h"
+#include "Error.hxx"
+#include "Domain.hxx"
+#include "util/Error.hxx"
+
+extern "C" {
+#include <libavutil/error.h>
+}
+
+void
+SetFfmpegError(Error &error, int errnum)
+{
+	char msg[256];
+	av_strerror(errnum, msg, sizeof(msg));
+	error.Set(ffmpeg_domain, errnum, msg);
+}
+
+void
+SetFfmpegError(Error &error, int errnum, const char *prefix)
+{
+	char msg[256];
+	av_strerror(errnum, msg, sizeof(msg));
+	error.Format(ffmpeg_domain, errnum, "%s: %s", prefix, msg);
+}

src/lib/ffmpeg/Error.hxx

@@ -0,0 +1,31 @@
+/*
+ * Copyright (C) 2003-2014 The Music Player Daemon Project
+ * http://www.musicpd.org
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#ifndef MPD_FFMPEG_ERROR_HXX
+#define MPD_FFMPEG_ERROR_HXX
+
+class Error;
+
+void
+SetFfmpegError(Error &error, int errnum);
+
+void
+SetFfmpegError(Error &error, int errnum, const char *prefix);
+
+#endif