@@ -50,6 +50,45 @@ VideoWriter::VideoWriter(const char *path, const char *filename, bool remuxing,
5050 }
5151}
5252
53+ void VideoWriter::initialize_audio (int sample_rate) {
54+ assert (this ->ofmt_ctx ->oformat ->audio_codec != AV_CODEC_ID_NONE); // check output format supports audio streams
55+ const AVCodec *audio_avcodec = avcodec_find_encoder (AV_CODEC_ID_AAC);
56+ assert (audio_avcodec);
57+ this ->audio_codec_ctx = avcodec_alloc_context3 (audio_avcodec);
58+ assert (this ->audio_codec_ctx );
59+ this ->audio_codec_ctx ->sample_fmt = AV_SAMPLE_FMT_FLTP;
60+ this ->audio_codec_ctx ->sample_rate = sample_rate;
61+ #if LIBAVUTIL_VERSION_INT >= AV_VERSION_INT(57, 28, 100) // FFmpeg 5.1+
62+ av_channel_layout_default (&this ->audio_codec_ctx ->ch_layout , 1 );
63+ #else
64+ this ->audio_codec_ctx ->channel_layout = AV_CH_LAYOUT_MONO;
65+ #endif
66+ this ->audio_codec_ctx ->bit_rate = 32000 ;
67+ this ->audio_codec_ctx ->flags |= AV_CODEC_FLAG_GLOBAL_HEADER;
68+ this ->audio_codec_ctx ->time_base = (AVRational){1 , audio_codec_ctx->sample_rate };
69+ int err = avcodec_open2 (this ->audio_codec_ctx , audio_avcodec, NULL );
70+ assert (err >= 0 );
71+ av_log_set_level (AV_LOG_WARNING); // hide "QAvg" info msgs at the end of every segment
72+
73+ this ->audio_stream = avformat_new_stream (this ->ofmt_ctx , NULL );
74+ assert (this ->audio_stream );
75+ err = avcodec_parameters_from_context (this ->audio_stream ->codecpar , this ->audio_codec_ctx );
76+ assert (err >= 0 );
77+
78+ this ->audio_frame = av_frame_alloc ();
79+ assert (this ->audio_frame );
80+ this ->audio_frame ->format = this ->audio_codec_ctx ->sample_fmt ;
81+ #if LIBAVUTIL_VERSION_INT >= AV_VERSION_INT(57, 28, 100) // FFmpeg 5.1+
82+ av_channel_layout_copy (&this ->audio_frame ->ch_layout , &this ->audio_codec_ctx ->ch_layout );
83+ #else
84+ this ->audio_frame ->channel_layout = this ->audio_codec_ctx ->channel_layout ;
85+ #endif
86+ this ->audio_frame ->sample_rate = this ->audio_codec_ctx ->sample_rate ;
87+ this ->audio_frame ->nb_samples = this ->audio_codec_ctx ->frame_size ;
88+ err = av_frame_get_buffer (this ->audio_frame , 0 );
89+ assert (err >= 0 );
90+ }
91+
5392void VideoWriter::write (uint8_t *data, int len, long long timestamp, bool codecconfig, bool keyframe) {
5493 if (of && data) {
5594 size_t written = util::safe_fwrite (data, 1 , len, of);
@@ -67,8 +106,10 @@ void VideoWriter::write(uint8_t *data, int len, long long timestamp, bool codecc
67106 }
68107 int err = avcodec_parameters_from_context (out_stream->codecpar , codec_ctx);
69108 assert (err >= 0 );
109+ // if there is an audio stream, it must be initialized before this point
70110 err = avformat_write_header (ofmt_ctx, NULL );
71111 assert (err >= 0 );
112+ header_written = true ;
72113 } else {
73114 // input timestamps are in microseconds
74115 AVRational in_timebase = {1 , 1000000 };
@@ -77,6 +118,7 @@ void VideoWriter::write(uint8_t *data, int len, long long timestamp, bool codecc
77118 av_init_packet (&pkt);
78119 pkt.data = data;
79120 pkt.size = len;
121+ pkt.stream_index = this ->out_stream ->index ;
80122
81123 enum AVRounding rnd = static_cast <enum AVRounding>(AV_ROUND_NEAR_INF|AV_ROUND_PASS_MINMAX);
82124 pkt.pts = pkt.dts = av_rescale_q_rnd (timestamp, in_timebase, ofmt_ctx->streams [0 ]->time_base , rnd);
@@ -95,11 +137,80 @@ void VideoWriter::write(uint8_t *data, int len, long long timestamp, bool codecc
95137 }
96138}
97139
140+ void VideoWriter::write_audio (uint8_t *data, int len, long long timestamp, int sample_rate) {
141+ if (!remuxing) return ;
142+ if (!audio_initialized) {
143+ initialize_audio (sample_rate);
144+ audio_initialized = true ;
145+ }
146+ if (!audio_codec_ctx) return ;
147+ // sync logMonoTime of first audio packet with the timestampEof of first video packet
148+ if (audio_pts == 0 ) {
149+ audio_pts = (timestamp * audio_codec_ctx->sample_rate ) / 1000000ULL ;
150+ }
151+
152+ // convert s16le samples to fltp and add to buffer
153+ const int16_t *raw_samples = reinterpret_cast <const int16_t *>(data);
154+ int sample_count = len / sizeof (int16_t );
155+ constexpr float normalizer = 1 .0f / 32768 .0f ;
156+
157+ const size_t max_buffer_size = sample_rate * 10 ; // 10 seconds
158+ if (audio_buffer.size () + sample_count > max_buffer_size) {
159+ size_t samples_to_drop = (audio_buffer.size () + sample_count) - max_buffer_size;
160+ LOGE (" Audio buffer overflow, dropping %zu oldest samples"
161+ audio_buffer.erase (audio_buffer.begin (), audio_buffer.begin () + samples_to_drop);
162+ audio_pts += samples_to_drop;
163+ }
164+
165+ // Add new samples to the buffer
166+ const size_t original_size = audio_buffer.size ();
167+ audio_buffer.resize (original_size + sample_count);
168+ std::transform (raw_samples, raw_samples + sample_count, audio_buffer.begin () + original_size,
169+ [](int16_t sample) { return sample * normalizer; });
170+
171+ if (!header_written) return ; // header not written yet, process audio frame after header is written
172+ while (audio_buffer.size () >= audio_codec_ctx->frame_size ) {
173+ audio_frame->pts = audio_pts;
174+ float *f_samples = reinterpret_cast <float *>(audio_frame->data [0 ]);
175+ std::copy (audio_buffer.begin (), audio_buffer.begin () + audio_codec_ctx->frame_size , f_samples);
176+ audio_buffer.erase (audio_buffer.begin (), audio_buffer.begin () + audio_codec_ctx->frame_size );
177+ encode_and_write_audio_frame (audio_frame);
178+ }
179+ }
180+
181+ void VideoWriter::encode_and_write_audio_frame (AVFrame* frame) {
182+ if (!remuxing || !audio_codec_ctx) return ;
183+ int send_result = avcodec_send_frame (audio_codec_ctx, frame); // encode frame
184+ if (send_result >= 0 ) {
185+ AVPacket *pkt = av_packet_alloc ();
186+ while (avcodec_receive_packet (audio_codec_ctx, pkt) == 0 ) {
187+ av_packet_rescale_ts (pkt, audio_codec_ctx->time_base , audio_stream->time_base );
188+ pkt->stream_index = audio_stream->index ;
189+
190+ int err = av_interleaved_write_frame (ofmt_ctx, pkt); // write encoded frame
191+ if (err < 0 ) {
192+ LOGW (" AUDIO: Write frame failed - error: %d"
193+ }
194+ av_packet_unref (pkt);
195+ }
196+ av_packet_free (&pkt);
197+ } else {
198+ LOGW (" AUDIO: Failed to send audio frame to encoder: %d"
199+ }
200+ audio_pts += audio_codec_ctx->frame_size ;
201+ }
202+
203+
98204VideoWriter::~VideoWriter () {
99205 if (this ->remuxing ) {
206+ if (this ->audio_codec_ctx ) {
207+ encode_and_write_audio_frame (NULL ); // flush encoder
208+ avcodec_free_context (&this ->audio_codec_ctx );
209+ }
100210 int err = av_write_trailer (this ->ofmt_ctx );
101211 if (err != 0 ) LOGE (" av_write_trailer failed %d"
102212 avcodec_free_context (&this ->codec_ctx );
213+ if (this ->audio_frame ) av_frame_free (&this ->audio_frame );
103214 err = avio_closep (&this ->ofmt_ctx ->pb );
104215 if (err != 0 ) LOGE (" avio_closep failed %d"
105216 avformat_free_context (this ->ofmt_ctx );
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