obs 源码解析笔记
2024-04-17 05:22:35
obs 源码解析笔记
obs源码编译
见我的另一篇文章：VS2017-OBS24.03源码编译
https://blog.csdn.net/weixin_44259356/article/details/102548121
obs源码简介
obs有两套源码，新版源码采用微内核思想，核心功能很少，大部分功能通过插件的方式实现，方便后续维护开发，这里我用的是最新版源码24.03。
插件模块头介绍
libobs / obs-module.h –用于创建插件模块的主要标头。该文件自动包括以下文件：
libobs / obs.h –主libobs标头。该文件自动包括以下文件：
libobs / obs-source.h –用于在插件模块中实现源代码
libobs / obs-output.h –用于在插件模块中实现输出
libobs / obs-encoder.h –用于在插件模块中实现编码器
libobs / obs-service.h –用于在插件模块中实现服务
libobs / obs-data.h –用于管理libobs对象的设置
libobs / obs-properties.h –用于为libobs对象生成属性
libobs / graphics / graphics.h –用于图形渲染
目录结构
结构如下：
其中比较重要的是：
ALL_BUILD
整个项目通过它来启动，直接启动obs会有部分文件找不到。
obs
主程序
obs-ffmpeg
obs通过调用ffmpeg api来实现推流录像等功能，以插件的方式实现
obs-x264
也是插件方式实现x264编码，这里后续如果要为obs增加编码方式比如h265等可以参考此插件源码
w32-pthreads
obs发送数据流线程，用的是另外一个开源项目，功能比较强大，详细信息可以打开源码注释查看，这里特别注意线程里的互斥锁，我在调试中很多obs的问题都是使用没有及时释放的资源引起的。
libobs
obs视频采集线程
推流部分关键函数源码简介
点击开始录制，obs将会调用ui部分代码读取录像设置参数：
位于\UI\window-basic-main-outputs.cpp
bool AdvancedOutput::StartRecording()
{const char *path;const char *recFormat;const char *filenameFormat;bool noSpace = false;bool overwriteIfExists = false;if (!useStreamEncoder) {if (!ffmpegOutput) {UpdateRecordingSettings();}} else if (!obs_output_active(streamOutput)) {UpdateStreamSettings();}UpdateAudioSettings();if (!Active())SetupOutputs();if (!ffmpegOutput || ffmpegRecording) {path = config_get_string(main->Config(), "AdvOut",ffmpegRecording ? "FFFilePath": "RecFilePath");recFormat = config_get_string(main->Config(), "AdvOut",ffmpegRecording ? "FFExtension": "RecFormat");filenameFormat = config_get_string(main->Config(), "Output","FilenameFormatting");overwriteIfExists = config_get_bool(main->Config(), "Output","OverwriteIfExists");noSpace = config_get_bool(main->Config(), "AdvOut",ffmpegRecording? "FFFileNameWithoutSpace": "RecFileNameWithoutSpace");os_dir_t *dir = path && path[0] ? os_opendir(path) : nullptr;if (!dir) {if (main->isVisible())OBSMessageBox::warning(main, QTStr("Output.BadPath.Title"),QTStr("Output.BadPath.Text"));elsemain->SysTrayNotify(QTStr("Output.BadPath.Text"),QSystemTrayIcon::Warning);return false;}os_closedir(dir);string strPath;strPath += path;char lastChar = strPath.back();if (lastChar != '/' && lastChar != '\\')strPath += "/";strPath += GenerateSpecifiedFilename(recFormat, noSpace,filenameFormat);ensure_directory_exists(strPath);if (!overwriteIfExists)FindBestFilename(strPath, noSpace);obs_data_t *settings = obs_data_create();obs_data_set_string(settings, ffmpegRecording ? "url" : "path",strPath.c_str());obs_output_update(fileOutput, settings);obs_data_release(settings);}if (!obs_output_start(fileOutput)) {QString error_reason;const char *error = obs_output_get_last_error(fileOutput);if (error)error_reason = QT_UTF8(error);elseerror_reason = QTStr("Output.StartFailedGeneric");QMessageBox::critical(main,QTStr("Output.StartRecordingFailed"),error_reason);return false;}return true;
}
读取完毕后，将参数应用于obs同时修改视频编码和音频编码设置，同时更新obs程序运行参数
inline void AdvancedOutput::SetupFFmpeg()
{const char *url = config_get_string(main->Config(), "AdvOut", "FFURL");int vBitrate = config_get_int(main->Config(), "AdvOut", "FFVBitrate");int gopSize = config_get_int(main->Config(), "AdvOut", "FFVGOPSize");bool rescale = config_get_bool(main->Config(), "AdvOut", "FFRescale");const char *rescaleRes =config_get_string(main->Config(), "AdvOut", "FFRescaleRes");const char *formatName =config_get_string(main->Config(), "AdvOut", "FFFormat");const char *mimeType =config_get_string(main->Config(), "AdvOut", "FFFormatMimeType");const char *muxCustom =config_get_string(main->Config(), "AdvOut", "FFMCustom");const char *vEncoder =config_get_string(main->Config(), "AdvOut", "FFVEncoder");int vEncoderId =config_get_int(main->Config(), "AdvOut", "FFVEncoderId");const char *vEncCustom =config_get_string(main->Config(), "AdvOut", "FFVCustom");int aBitrate = config_get_int(main->Config(), "AdvOut", "FFABitrate");int aMixes = config_get_int(main->Config(), "AdvOut", "FFAudioMixes");const char *aEncoder =config_get_string(main->Config(), "AdvOut", "FFAEncoder");int aEncoderId =config_get_int(main->Config(), "AdvOut", "FFAEncoderId");const char *aEncCustom =config_get_string(main->Config(), "AdvOut", "FFACustom");obs_data_t *settings = obs_data_create();obs_data_set_string(settings, "url", url);obs_data_set_string(settings, "format_name", formatName);obs_data_set_string(settings, "format_mime_type", mimeType);obs_data_set_string(settings, "muxer_settings", muxCustom);obs_data_set_int(settings, "gop_size", gopSize);obs_data_set_int(settings, "video_bitrate", vBitrate);obs_data_set_string(settings, "video_encoder", vEncoder);obs_data_set_int(settings, "video_encoder_id", vEncoderId);obs_data_set_string(settings, "video_settings", vEncCustom);obs_data_set_int(settings, "audio_bitrate", aBitrate);obs_data_set_string(settings, "audio_encoder", aEncoder);obs_data_set_int(settings, "audio_encoder_id", aEncoderId);obs_data_set_string(settings, "audio_settings", aEncCustom);if (rescale && rescaleRes && *rescaleRes) {int width;int height;int val = sscanf(rescaleRes, "%dx%d", &width, &height);if (val == 2 && width && height) {obs_data_set_int(settings, "scale_width", width);obs_data_set_int(settings, "scale_height", height);}}obs_output_set_mixers(fileOutput, aMixes);obs_output_set_media(fileOutput, obs_get_video(), obs_get_audio());obs_output_update(fileOutput, settings);obs_data_release(settings);
}
参数设置成功后开始准备输出，位于：\libobs\obs-output.c
bool obs_output_start(obs_output_t *output)
{bool encoded;bool has_service;if (!obs_output_valid(output, "obs_output_start"))return false;if (!output->context.data)return false;has_service = (output->info.flags & OBS_OUTPUT_SERVICE) != 0;if (has_service && !obs_service_initialize(output->service, output))return false;encoded = (output->info.flags & OBS_OUTPUT_ENCODED) != 0;if (encoded && output->delay_sec) {return obs_output_delay_start(output);} else {if (obs_output_actual_start(output)) {do_output_signal(output, "starting");return true;}return false;}
}
输出流准备好了之后，创建输出函数线程，开始调用ffmpeg有关函数准备输出。位于\obs-ffmpeg\obs-ffmpeg-output.c
static bool ffmpeg_output_start(void *data)
{struct ffmpeg_output *output = data;int ret;if (output->connecting)return false;os_atomic_set_bool(&output->stopping, false);output->audio_start_ts = 0;output->video_start_ts = 0;output->total_bytes = 0;ret = pthread_create(&output->start_thread, NULL, start_thread, output);return (output->connecting = (ret == 0));
}
然后创建ffmpeg输出，设置输出参数，
**avformat_alloc_output_context2(&data->output, output_format, NULL,NULL);**
上面是调用ffmpeg关键代码设置输出方式，如rtp，rtmp等。下面是完整函数。
static bool ffmpeg_data_init(struct ffmpeg_data *data,struct ffmpeg_cfg *config)
{bool is_rtmp = false;memset(data, 0, sizeof(struct ffmpeg_data));data->config = *config;data->num_audio_streams = config->audio_mix_count;data->audio_tracks = config->audio_tracks;if (!config->url || !*config->url)return false;#if LIBAVCODEC_VERSION_INT < AV_VERSION_INT(58, 9, 100)av_register_all();
#endifavformat_network_init();is_rtmp = (astrcmpi_n(config->url, "rtmp://", 7) == 0);AVOutputFormat *output_format = av_guess_format(is_rtmp ? "flv" : data->config.format_name, data->config.url,is_rtmp ? NULL : data->config.format_mime_type);if (output_format == NULL) {ffmpeg_log_error(LOG_WARNING, data,"Couldn't find matching output format with ""parameters: name=%s, url=%s, mime=%s",safe_str(is_rtmp ? "flv" : data->config.format_name),safe_str(data->config.url),safe_str(is_rtmp ? NULL: data->config.format_mime_type));goto fail;}avformat_alloc_output_context2(&data->output, output_format, NULL,NULL);if (!data->output) {ffmpeg_log_error(LOG_WARNING, data,"Couldn't create avformat context");goto fail;}if (is_rtmp) {data->output->oformat->video_codec = AV_CODEC_ID_H264;data->output->oformat->audio_codec = AV_CODEC_ID_AAC;} else {if (data->config.format_name)set_encoder_ids(data);}if (!init_streams(data))goto fail;if (!open_output_file(data))goto fail;av_dump_format(data->output, 0, NULL, 1);data->initialized = true;return true;fail:blog(LOG_WARNING, "ffmpeg_data_init failed");return false;
}
写入文件头，调用ffmpeg函数代码为：
ret = avformat_write_header(data->output, &dict);
以下为完整函数代码：
static inline bool open_output_file(struct ffmpeg_data *data)
{AVOutputFormat *format = data->output->oformat;int ret;AVDictionary *dict = NULL;if ((ret = av_dict_parse_string(&dict, data->config.muxer_settings, "="," ", 0))) {ffmpeg_log_error(LOG_WARNING, data,"Failed to parse muxer settings: %s\n%s",av_err2str(ret), data->config.muxer_settings);av_dict_free(&dict);return false;}if (av_dict_count(dict) > 0) {struct dstr str = {0};AVDictionaryEntry *entry = NULL;while ((entry = av_dict_get(dict, "", entry,AV_DICT_IGNORE_SUFFIX)))dstr_catf(&str, "\n\t%s=%s", entry->key, entry->value);blog(LOG_INFO, "Using muxer settings: %s", str.array);dstr_free(&str);}if ((format->flags & AVFMT_NOFILE) == 0) {ret = avio_open2(&data->output->pb, data->config.url,AVIO_FLAG_WRITE, NULL, &dict);if (ret < 0) {ffmpeg_log_error(LOG_WARNING, data,"Couldn't open '%s', %s",data->config.url, av_err2str(ret));av_dict_free(&dict);return false;}}strncpy(data->output->filename, data->config.url,sizeof(data->output->filename));data->output->filename[sizeof(data->output->filename) - 1] = 0;ret = avformat_write_header(data->output, &dict);if (ret < 0) {ffmpeg_log_error(LOG_WARNING, data, "Error opening '%s': %s",data->config.url, av_err2str(ret));return false;}if (av_dict_count(dict) > 0) {struct dstr str = {0};AVDictionaryEntry *entry = NULL;while ((entry = av_dict_get(dict, "", entry,AV_DICT_IGNORE_SUFFIX)))dstr_catf(&str, "\n\t%s=%s", entry->key, entry->value);blog(LOG_INFO, "Invalid muxer settings: %s", str.array);dstr_free(&str);}av_dict_free(&dict);return true;
}
创建数据线程，设置视频流，音频流编码，然后捕获数据流开始输出
static bool try_connect(struct ffmpeg_output *output)
{video_t *video = obs_output_video(output->output);const struct video_output_info *voi = video_output_get_info(video);struct ffmpeg_cfg config;obs_data_t *settings;bool success;int ret;settings = obs_output_get_settings(output->output);obs_data_set_default_int(settings, "gop_size", 120);config.url = obs_data_get_string(settings, "url");config.format_name = get_string_or_null(settings, "format_name");config.format_mime_type =get_string_or_null(settings, "format_mime_type");config.muxer_settings = obs_data_get_string(settings, "muxer_settings");config.video_bitrate = (int)obs_data_get_int(settings, "video_bitrate");config.audio_bitrate = (int)obs_data_get_int(settings, "audio_bitrate");config.gop_size = (int)obs_data_get_int(settings, "gop_size");config.video_encoder = get_string_or_null(settings, "video_encoder");config.video_encoder_id =(int)obs_data_get_int(settings, "video_encoder_id");config.audio_encoder = get_string_or_null(settings, "audio_encoder");config.audio_encoder_id =(int)obs_data_get_int(settings, "audio_encoder_id");config.video_settings = obs_data_get_string(settings, "video_settings");config.audio_settings = obs_data_get_string(settings, "audio_settings");config.scale_width = (int)obs_data_get_int(settings, "scale_width");config.scale_height = (int)obs_data_get_int(settings, "scale_height");config.width = (int)obs_output_get_width(output->output);config.height = (int)obs_output_get_height(output->output);config.format =obs_to_ffmpeg_video_format(video_output_get_format(video));config.audio_tracks = (int)obs_output_get_mixers(output->output);config.audio_mix_count = get_audio_mix_count(config.audio_tracks);if (format_is_yuv(voi->format)) {config.color_range = voi->range == VIDEO_RANGE_FULL? AVCOL_RANGE_JPEG: AVCOL_RANGE_MPEG;config.color_space = voi->colorspace == VIDEO_CS_709? AVCOL_SPC_BT709: AVCOL_SPC_BT470BG;} else {config.color_range = AVCOL_RANGE_UNSPECIFIED;config.color_space = AVCOL_SPC_RGB;}if (config.format == AV_PIX_FMT_NONE) {blog(LOG_DEBUG, "invalid pixel format used for FFmpeg output");return false;}if (!config.scale_width)config.scale_width = config.width;if (!config.scale_height)config.scale_height = config.height;success = ffmpeg_data_init(&output->ff_data, &config);obs_data_release(settings);if (!success) {if (output->ff_data.last_error) {obs_output_set_last_error(output->output,output->ff_data.last_error);}ffmpeg_data_free(&output->ff_data);return false;}struct audio_convert_info aci = {.format =output->ff_data.audio_format};output->active = true;if (!obs_output_can_begin_data_capture(output->output, 0))return false;ret = pthread_create(&output->write_thread, NULL, write_thread, output);if (ret != 0) {ffmpeg_log_error(LOG_WARNING, &output->ff_data,"ffmpeg_output_start: failed to create write ""thread.");ffmpeg_output_full_stop(output);return false;}obs_output_set_video_conversion(output->output, NULL);obs_output_set_audio_conversion(output->output, &aci);obs_output_begin_data_capture(output->output, 0);output->write_thread_active = true;return true;
}
线程设置完毕后，开始通过线程写入数据，输出
static void *write_thread(void *data)
{struct ffmpeg_output *output = data;while (os_sem_wait(output->write_sem) == 0) {/* check to see if shutting down */if (os_event_try(output->stop_event) == 0)break;int ret = process_packet(output);if (ret != 0) {int code = OBS_OUTPUT_ERROR;pthread_detach(output->write_thread);output->write_thread_active = false;if (ret == -ENOSPC)code = OBS_OUTPUT_NO_SPACE;obs_output_signal_stop(output->output, code);ffmpeg_deactivate(output);break;}}output->active = false;return NULL;
}
线程将反复调用下面函数处理数据包，注意这里线程有互斥锁判断，修改不当容易造成程序崩溃。
static int process_packet(struct ffmpeg_output *output)
{AVPacket packet;bool new_packet = false;int ret;pthread_mutex_lock(&output->write_mutex);if (output->packets.num) {packet = output->packets.array[0];da_erase(output->packets, 0);new_packet = true;}pthread_mutex_unlock(&output->write_mutex);if (!new_packet)return 0;/*blog(LOG_DEBUG, "size = %d, flags = %lX, stream = %d, ""packets queued: %lu",packet.size, packet.flags,packet.stream_index, output->packets.num);*/if (stopping(output)) {uint64_t sys_ts = get_packet_sys_dts(output, &packet);if (sys_ts >= output->stop_ts) {ffmpeg_output_full_stop(output);return 0;}}output->total_bytes += packet.size;ret = av_interleaved_write_frame(output->ff_data.output, &packet);if (ret < 0) {av_free_packet(&packet);ffmpeg_log_error(LOG_WARNING, &output->ff_data,"receive_audio: Error writing packet: %s",av_err2str(ret));return ret;}return 0;
}
点击停止录制后，线程将会一步步释放资源。工作涉及整个流程大体如上，后续可能会补充。
附录国人写的一个ffmpeg官方函数调用实现rtmp或者rtp数据传输开源项目：
https://github.com/leixiaohua1020/simplest_ffmpeg_streamer/blob/master/simplest_ffmpeg_streamer/simplest_ffmpeg_streamer.cpp
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