Show FFmpeg driver errors when hardware encoding fails

tools/chatgui/src/live_video_encoder.cpp

@@ -2,6 +2,7 @@
 #include "video_codec_log.h"
 #include <QElapsedTimer>
 #include <QPainter>
+#include <QStringList>
 #include <algorithm>
 #include <cstdlib>
 #include <cstring>
@@ -151,11 +152,13 @@ bool LiveVideoEncoder::open(const LiveVideoConfig& config, Backend backend) {
     }
 #ifdef HAVE_FFMPEG
     video_ffmpeg_init();
+    QStringList failures;
     for (const auto& name : encoders(config.codec)) {
         if (!matchesBackend(name, backend)) continue;
         if (!config.backend.isEmpty() && name != config.backend.toLatin1()) continue;
         const AVCodec* encoder = avcodec_find_encoder_by_name(name.constData());
         if (!encoder) continue;
+        VideoCodecErrors diagnostics;
         // Проба не оставляет references/PTS в live-контексте: после двух KEY encoder открывается заново.
         for (int pass = 0; pass < 2; pass++) {
             close(); m->config = config; m->name = QString::fromLatin1(name);
@@ -365,7 +368,14 @@ bool LiveVideoEncoder::open(const LiveVideoConfig& config, Backend backend) {
                 c->thread_count, c->active_thread_type);
             return true;
         }
+        QString reason = m->error;
+        const QString details = QString::fromUtf8(diagnostics.text()).trimmed();
+        if (!details.isEmpty() && details != reason) reason += '\n' + details;
+        failures.append(QString::fromLatin1(name) + ": " + reason);
+        CODEC_LOG(DEBUG_LEVEL_WARN, DEBUG_CATEGORY_VIDEO, "desktop encoder attempt failed name=%s reason=%s",
+            name.constData(), qPrintable(reason));
     }
+    if (!failures.isEmpty()) m->error = failures.join("\n\n");
     if (m->error.isEmpty()) m->error = "No working encoder for " + codecName(config.codec);
 #else
     m->error = "FFmpeg is unavailable";