From 147a2d38463d983ec7c66ef5c4c9c6cce7d52787 Mon Sep 17 00:00:00 2001 From: "Steinar H. Gunderson" Date: Wed, 5 Dec 2018 20:20:08 +0100 Subject: [PATCH] Add a hack to FFmpegCapture for decoding Futatabi's Y'CbCr streams correctly. --- nageru/ffmpeg_capture.cpp | 20 +++++++++++++++++--- nageru/ffmpeg_capture.h | 1 + 2 files changed, 18 insertions(+), 3 deletions(-) diff --git a/nageru/ffmpeg_capture.cpp b/nageru/ffmpeg_capture.cpp index e5cb096..c8b87fe 100644 --- a/nageru/ffmpeg_capture.cpp +++ b/nageru/ffmpeg_capture.cpp @@ -134,7 +134,7 @@ AVPixelFormat decide_dst_format(AVPixelFormat src_format, bmusb::PixelFormat dst return av_get_pix_fmt(best_format); } -YCbCrFormat decode_ycbcr_format(const AVPixFmtDescriptor *desc, const AVFrame *frame) +YCbCrFormat decode_ycbcr_format(const AVPixFmtDescriptor *desc, const AVFrame *frame, bool is_mjpeg) { YCbCrFormat format; AVColorSpace colorspace = av_frame_get_colorspace(frame); @@ -198,6 +198,17 @@ YCbCrFormat decode_ycbcr_format(const AVPixFmtDescriptor *desc, const AVFrame *f break; } + if (is_mjpeg && !format.full_range) { + // Limited-range MJPEG is only detected by FFmpeg whenever a special + // JPEG comment is set, which means that in practice, the stream is + // almost certainly generated by Futatabi. Override FFmpeg's forced + // MJPEG defaults (it disregards the values set in the mux) with what + // Futatabi sets. + format.luma_coefficients = YCBCR_REC_709; + format.cb_x_position = 0.0; + format.cb_y_position = 0.5; + } + format.cr_x_position = format.cb_x_position; format.cr_y_position = format.cb_y_position; return format; @@ -404,6 +415,9 @@ bool FFmpegCapture::play_video(const string &pathname) unique_ptr video_codec_ctx_cleanup( video_codec_ctx.get(), avcodec_close); + // Used in decode_ycbcr_format(). + is_mjpeg = video_codecpar->codec_id == AV_CODEC_ID_MJPEG; + // Open audio decoder, if we have audio. AVCodecContextWithDeleter audio_codec_ctx; if (audio_stream_index != -1) { @@ -848,7 +862,7 @@ UniqueFrame FFmpegCapture::make_video_frame(const AVFrame *frame, const string & video_frame->len = (width * 2) * height; const AVPixFmtDescriptor *desc = av_pix_fmt_desc_get(sws_dst_format); - current_frame_ycbcr_format = decode_ycbcr_format(desc, frame); + current_frame_ycbcr_format = decode_ycbcr_format(desc, frame, is_mjpeg); } else { assert(pixel_format == bmusb::PixelFormat_8BitYCbCrPlanar); const AVPixFmtDescriptor *desc = av_pix_fmt_desc_get(sws_dst_format); @@ -867,7 +881,7 @@ UniqueFrame FFmpegCapture::make_video_frame(const AVFrame *frame, const string & video_frame->len = width * height + 2 * chroma_width * chroma_height; - current_frame_ycbcr_format = decode_ycbcr_format(desc, frame); + current_frame_ycbcr_format = decode_ycbcr_format(desc, frame, is_mjpeg); } sws_scale(sws_ctx.get(), frame->data, frame->linesize, 0, frame->height, pic_data, linesizes); diff --git a/nageru/ffmpeg_capture.h b/nageru/ffmpeg_capture.h index 31e94ab..b0a1be2 100644 --- a/nageru/ffmpeg_capture.h +++ b/nageru/ffmpeg_capture.h @@ -255,6 +255,7 @@ private: int sws_last_width = -1, sws_last_height = -1, sws_last_src_format = -1; AVPixelFormat sws_dst_format = AVPixelFormat(-1); // In practice, always initialized. AVRational video_timebase, audio_timebase; + bool is_mjpeg = false; QuittableSleeper producer_thread_should_quit; std::thread producer_thread; -- 2.39.2