[multimedia/haruna] src/transcript: transcript: add subtitle parser

Git commit c8708e39ff63c883277855420a6b7efe7241aaf9 by George Florea Bănuș, on behalf of M. Sadık Uğursoy.
Committed on 18/07/2026 at 22:47.
Pushed by georgefb into branch 'master'.

transcript: add subtitle parser

M  +13   -0    src/transcript/CMakeLists.txt
A  +21   -0    src/transcript/subtitleline.h     [License: GPL(v3.0+)]
A  +161  -0    src/transcript/subtitleparser.cpp     [License: GPL(v3.0+)]
A  +30   -0    src/transcript/subtitleparser.h     [License: GPL(v3.0+)]

https://invent.kde.org/multimedia/haruna/-/commit/c8708e39ff63c883277855420a6b7efe7241aaf9

diff --git a/src/transcript/CMakeLists.txt b/src/transcript/CMakeLists.txt
index 814118a6..236c0cca 100644
--- a/src/transcript/CMakeLists.txt
+++ b/src/transcript/CMakeLists.txt
@@ -12,8 +12,21 @@ qt_add_qml_module(transcript
     IMPORT_PATH ${CMAKE_BINARY_DIR}
     QML_FILES
         Transcript.qml
+    SOURCES
+        subtitleline.h
+        subtitleparser.h
+        subtitleparser.cpp
+)
+
+target_include_directories(transcript
+    PRIVATE
+        ${AVCODEC_INCLUDE_DIRS}
 )
 
 target_link_libraries(transcript PRIVATE
     Qt6::Core
+
+    KF6::FileMetaData
+
+    utilitiesplugin
 )
diff --git a/src/transcript/subtitleline.h b/src/transcript/subtitleline.h
new file mode 100644
index 00000000..459a1677
--- /dev/null
+++ b/src/transcript/subtitleline.h
@@ -0,0 +1,21 @@
+/*
+ * SPDX-FileCopyrightText: 2026 Muhammet Sadık Uğursoy <[email protected]>
+ *
+ * SPDX-License-Identifier: GPL-3.0-or-later
+ */
+
+#ifndef SUBTITLELINE_H
+#define SUBTITLELINE_H
+
+#include <QString>
+
+struct SubtitleLine {
+    QString text;
+    double startTime;
+    double endTime;
+    QString formattedStartTime;
+    QString formattedEndTime;
+    double duration;
+};
+
+#endif // SUBTITLELINE_H
diff --git a/src/transcript/subtitleparser.cpp b/src/transcript/subtitleparser.cpp
new file mode 100644
index 00000000..a39464e4
--- /dev/null
+++ b/src/transcript/subtitleparser.cpp
@@ -0,0 +1,161 @@
+/*
+ * SPDX-FileCopyrightText: 2026 Muhammet Sadık Uğursoy <[email protected]>
+ *
+ * SPDX-License-Identifier: GPL-3.0-or-later
+ */
+
+#include "subtitleparser.h"
+
+#include <QRegularExpression>
+#include <QString>
+#include <QUrl>
+
+#include "miscutils.h"
+#include "subtitleline.h"
+extern "C" {
+#include <libavcodec/avcodec.h>
+#include <libavformat/avformat.h>
+}
+
+using namespace Qt::StringLiterals;
+
+SubtitleParser::SubtitleParser(QObject *parent)
+    : QObject{parent}
+{
+}
+
+void SubtitleParser::parseSubtitle(const QUrl &url, const int streamIndex)
+{
+    if (!url.isLocalFile()) {
+        return;
+    }
+
+    QString path = url.toLocalFile();
+
+    AVFormatContext *fmt_ctx = avformat_alloc_context();
+    if (!fmt_ctx) {
+        return;
+    }
+
+    if (avformat_open_input(&fmt_ctx, path.toUtf8().data(), nullptr, nullptr) < 0) {
+        avformat_free_context(fmt_ctx);
+        return;
+    }
+
+    if (avformat_find_stream_info(fmt_ctx, nullptr) < 0) {
+        avformat_close_input(&fmt_ctx);
+        return;
+    }
+
+    // Initialize the subtitle decoder
+    const AVCodecParameters *codecpar = fmt_ctx->streams[streamIndex]->codecpar;
+    const AVCodec *decoder = avcodec_find_decoder(codecpar->codec_id);
+    if (!decoder) {
+        avformat_close_input(&fmt_ctx);
+        return;
+    }
+
+    AVCodecContext *codecContext = avcodec_alloc_context3(decoder);
+    if (!codecContext) {
+        avformat_close_input(&fmt_ctx);
+        return;
+    }
+
+    if (avcodec_parameters_to_context(codecContext, codecpar) < 0) {
+        avcodec_free_context(&codecContext);
+        avformat_close_input(&fmt_ctx);
+        return;
+    }
+
+    if (avcodec_open2(codecContext, decoder, nullptr) < 0) {
+        avcodec_free_context(&codecContext);
+        avformat_close_input(&fmt_ctx);
+        return;
+    }
+
+    // Read the subtitle data from the codex context
+    AVPacket *packet = av_packet_alloc();
+    if (!packet) {
+        avcodec_free_context(&codecContext);
+        avformat_close_input(&fmt_ctx);
+        return;
+    }
+
+    AVSubtitle subtitle;
+    const AVRational timeBase = fmt_ctx->streams[streamIndex]->time_base;
+    double timeMultiplier = 1.0 * timeBase.num / timeBase.den;
+    int gotSub = 0;
+    while (av_read_frame(fmt_ctx, packet) >= 0) {
+        if (packet->stream_index == int(streamIndex)) {
+            // Decode the subtitle packet
+            int ret = avcodec_decode_subtitle2(codecContext, &subtitle, &gotSub, packet);
+
+            if (ret >= 0 && gotSub != 0) {
+                int64_t startSecs = packet->pts;
+                int64_t duration = packet->duration;
+                int64_t endSecs = startSecs + duration;
+
+                QString text;
+                QString line;
+
+                for (unsigned int i = 0; i < subtitle.num_rects; i++) {
+                    // Note: Even though SUBTITLE_ASS sounds like they are for ASS/SSA only, that is not true.
+                    // Most modern subtitles are handled as SUBTITLE_ASS (srt, sub, ssa, ass, smi) by FFMpeg internally.
+                    // SUBTITLE_TEXT is only used by very simple legacy formats that have no styling capabilities.
+                    switch (subtitle.rects[i]->type) {
+                    case SUBTITLE_TEXT: {
+                        line = QString::fromUtf8(subtitle.rects[i]->text);
+                        break;
+                    }
+                    case SUBTITLE_ASS: {
+                        line = QString::fromUtf8(subtitle.rects[i]->ass);
+                        line = formatASS(line);
+                        break;
+                    }
+                    case SUBTITLE_BITMAP:
+                    case SUBTITLE_NONE: {
+                        break;
+                    }
+                    }
+
+                    text.append(line);
+                }
+
+                SubtitleLine transcriptItem;
+                transcriptItem.text = text;
+                transcriptItem.duration = duration;
+                transcriptItem.startTime = startSecs;
+                transcriptItem.endTime = endSecs;
+                transcriptItem.formattedStartTime = MiscUtils::formatTime(startSecs * timeMultiplier);
+                transcriptItem.formattedEndTime = MiscUtils::formatTime(endSecs * timeMultiplier);
+                Q_EMIT transcriptItemReady(transcriptItem, streamIndex);
+
+                // must be freed when gotSub is set
+                avsubtitle_free(&subtitle);
+            }
+        }
+        av_packet_unref(packet);
+    }
+
+    av_packet_free(&packet);
+    avcodec_free_context(&codecContext);
+    avformat_close_input(&fmt_ctx);
+}
+
+QString SubtitleParser::formatASS(const QString in)
+{
+    // libavc returns the parsed text as a comma separated line, consists of 8 headers and lastly, the text
+    // The text is always guaranteed to be the last one since it can contain commas.
+    // We need to skip the first 8 columns and join the rest.
+    QString text = in.section(QChar::fromLatin1(','), 8);
+
+    // Remove markup text
+    QRegularExpression re(u"\\{[^}]*\\}"_s);
+    while (re.match(text).hasMatch()) {
+        text.remove(re);
+    }
+    // FFMpeg decoder adds \\N as newline for ASS type.
+    text.replace(u"\\N"_s, u"\n"_s, Qt::CaseSensitive);
+
+    return QString::fromUtf8(text.toUtf8());
+}
diff --git a/src/transcript/subtitleparser.h b/src/transcript/subtitleparser.h
new file mode 100644
index 00000000..d2f9a64c
--- /dev/null
+++ b/src/transcript/subtitleparser.h
@@ -0,0 +1,30 @@
+/*
+ * SPDX-FileCopyrightText: 2026 Muhammet Sadık Uğursoy <[email protected]>
+ *
+ * SPDX-License-Identifier: GPL-3.0-or-later
+ */
+
+#ifndef SUBTITLEPARSER_H
+#define SUBTITLEPARSER_H
+
+#include <QObject>
+
+struct SubtitleLine;
+
+class SubtitleParser : public QObject
+{
+    Q_OBJECT
+
+public:
+    explicit SubtitleParser(QObject *parent = nullptr);
+
+    void parseSubtitle(const QUrl &url, const int streamIndex);
+
+Q_SIGNALS:
+    void transcriptItemReady(const SubtitleLine &item, const int streamIndex);
+
+private:
+    QString formatASS(const QString in);
+};
+
+#endif // SUBTITLEPARSER_H