March 2014 - ffmpeg-user - lists.ffmpeg.org

Syncing clips based on audio waveform?
by Arthur Wait 05 Oct '17

05 Oct '17

Hi all, This is coming from out of left field I imagine, but I'm wondering if anyone knows of a filter (or chain of filters) which would allow me to align/sync two video clips based on matches in their audio waveforms. I'm shooting events with multiple cameras and would like to either trim the clips to a precise, matching starting frame or generate a metadata "offset" marker indicating how far off one clip is from the other in time. Then I can trim the clips to match. Is this possible in ffmpeg (or anywhere else for that matter!)? Thanks very much! Art

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Compiling FFMPEG with ffplay support
by Stas Oskin 14 Jun '17

14 Jun '17

Hi. Did the compilation parameters changed in recent FFMPEG version? Configuring the FFMPEG like this: ./configure --prefix=/usr --enable-pthreads Does not produce ffplay anymore. I tried to add --enable-ffplay, without any result. Any idea what I'm missing? Thanks.

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How do I encode DVB Subtitles?
by Wagner Patriota 02 May '17

02 May '17

*QUESTION 1:* How do I add a STR file to a MPEG-TS file with the "DVB subtitle codec"? If so, could you give me a sample command line? Thank. I am trying: ffmpeg -i video.ts *-i subtitle.srt* -vcodec copy -acodec copy *-scodec dvbsub* output.ts The stream is created because I can see it with MediaInfo, but the subtitles don't appear! *QUESTION 2:* How do I use the command *slang*? I try to use it, but ffmpeg says the command doesn't exist. Thank you.

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How to use global_header, fflags, rtpflags parameter.
by Ly Tran Cong 06 Dec '16

06 Dec '16

Hello, Can anyone tell me how to use flags +global_header, fflags +latm, rtpflags +latm Which parameter using with video encode and which parameter using with audio encode. Thanks -- Regards, Tran Ly Vega Corporation 98 Hoang Quoc Viet Str, Hanoi, Vietnam Tel: 84 4 755 4190 Fax: 84 4 755 4190 Mobile: 84 91 487 1115 www.vega.com.vn; www.clip.vn; www.chacha.vn; www.ringring.vn

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Flip in sws_scale
by romulo.fernandes＠gmail.com 11 Mar '16

11 Mar '16

Hello, I'm using libswscale to scale and convert pixel format from frames that I capture from the screen. In my windows build the frames that I capture are in DIB format. I'm using FFMPEG SVN rev 16437. Calling sws_scale normally I get the image correctly, except that it's vertically flipped. If I change the srcSliceY from 0 to srcHeight and srcSliceH from srcHeight to 0, I get a grey image (with correct dimensions). If I keep the srcSliceY in 0 and change srcSliceH from srcHeight to -srcHeight, I also get that grey image. Is there a way to make sws_scale flip the image for me ?

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Howto compile ffplay.c in seperate directory with my own svn-version of ffmpeg
by tps＠netmaster.dk 24 Feb '16

24 Feb '16

Dear All I have compiled svn-version of ffmpeg. I only do configure and make. I do not do make install because I don't want this svn-version of ffmpeg to overwrite the 'official' Ubuntu version of ffpeg that is also on the host. Now I want to compile my own version of ffplay.c so I create a directory ffplay at the same level as the svn ffmpeg-directory. I copy ffplay.c from ffmpeg to ffplay. Now what gcc options should I use to compile ffplay.c? I tried with this but got tons of errors: gcc -o ffplay ffplay.c -I../ffmpeg -L../ffmpeg/libavcodec -L../ffmpeg/libavformt -L../ffmpeg/libswscale -L../ffmpeg/libavutil -lavcodec -lavformat -lswscale -lavutil -lmp3lame -lx264 `sdl-config --cflags --libs` I note that when I do the make in the svn ffmpeg-directory there are a lot of options on the gcc command. I hardly know any of the options. Thanks in advance

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a -vf for broadcast safe
by Jim Shupert 30 Dec '15

30 Dec '15

I was wondering if there is a means to ensure that a file is transcoded as 'broadcast safe' input a unCompressed yuv avi and get a second Uncompressed yuv avi or mov and it would be 'broadcast safe'. I wish for the functionality of the broadcast safe effect available withing final cut 6. I do not find anything in the documentation. I wonder if Hald CLUT would be of any utility. thanks jim s

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timestamp calculation
by Chau Pham 25 Jun '15

25 Jun '15

Hi Everybody, Suppose that I know AVPacket element: pts, dts, duration How could I calculate the timestamp (hh:mm:ss:MMM)? Thank You,Chau Pham.

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Problem in FFMPEG 1.1
by Simone Cercignani 14 Apr '15

14 Apr '15

Hi, I am trying to compile ffmpeg 1.1 with: ./configure --toolchain=msvc I have followed the instruction at: https://ffmpeg.org/platform.html#Microsoft-Visual-C_002b_002b but after that command: Simone@Simone-PC /c/Jobs/ffmpeg-1.1 $ ./configure toolchain=msvc c99wrap cl is unable to create an executable file. If c99wrap cl is a cross-compiler, use the --enable-cross-compile option. Only do this if you know what cross compiling means. C compiler test failed. If you think configure made a mistake, make sure you are using the latest version from Git. If the latest version fails, report the problem to the ffmpeg-user(a)ffmpeg.org mailing list or IRC #ffmpeg on irc.freenode.net. Include the log file "config.log" produced by configure as this will help solving the problem. Simone@Simone-PC /c/Jobs/ffmpeg-1.1 $ in attachment the "config.log" file.... Thanks in advance Simone

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Converting MPEG-TS to MKV with hard coded subtitles produces error message
by Stuart 09 Apr '15

09 Apr '15

Hello, I want to convert an MPEG-TS from a Humax PVR to a MKV with H.264 encoded video with hard coded DVB subtitles. Unfortunately, having downloaded a build from ffmpeg.zeranoe.com, instead of hard coded subtitles I am getting "sub2video: rectangle overflowing" messages. I've tweaked ffmpeg.c to display the parameters causing the message and built a cut down ffmpeg. (I have built a toolchain using Zeranoe's build script and built libogg, libvorbis, libx264 and pthreads-win32 from source). The message is output because the video stream is 704x576 but the subtitle rectangles are 720 wide. If I tweak function sub2video_prepare in ffmpeg_filter.c to hard code the canvas width and height to be 720 and 576 respectively then I can produce an MKV with hard coded DVB subtitles with the command: ffmpeg -i in.TS -filter_complex "[0:v]pad=720:576[main];[main][0:s]overlay" -sn out.MKV I've tried cropping the subtitle stream before overlaying but still get the "sub2video: rectangle overflowing" messages with the Zeranoe build. I've also tried scaling the video stream and padding the video stream. I think the canvas size is assigned equal to the video stream size before applying the filters. Hence, scaling or padding the video stream doesn't increase the canvas size to match the subtitle rectangle dimensions. Is there a filter sequence that would accommodate the subtitle rectangle dimensions being larger than the video stream dimensions? Or does the sub2video "hack" not cater for this situation? Many thanks, Stu

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