August 2020 - ffmpeg-user - lists.ffmpeg.org

Getting audio correct (Zoom meeting)
by Cecil Westerhof 15 Aug '20

15 Aug '20

I have to publish zoom recordings. One of the problems is that audio is out of sync. And it is different for the different recordings. It goes from something I notice because I am a nitpicker, to something I think will annoy everyone. Is that something that is just part of recording Zoom meetings (hardware and internet connection of the sender), or can it be mend without to much difficulty? -- Cecil Westerhof Senior Software Engineer LinkedIn: http://www.linkedin.com/in/cecilwesterhof

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does ffmpeg support fdk-aac 2.0.1
by qw 14 Aug '20

14 Aug '20

Hi, does ffmpeg support fdk-aac 2.0.1? Thanks regards Andrew

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Slowing ffmpeg down
by Rich Andrews 13 Aug '20

13 Aug '20

Is there any trick to slow down ffmpeg on a simple stream mapping? Stream mapping: Stream #0:0 -> #0:0 (pcm_s16le (native) -> pcm_s16le (native)) Given an input file that is looped and output with a command such as: ffmpeg-4.2.1-armhf-static/ffmpeg -y -t 200 -stream_loop -1 -i HoldMusic.wav -map 0:a:0 -f wav output.wav ffmpeg can move the data really quickly! bitrate=1411.2kbits/s speed= 262x Any way to get that speed down to ~1x? My purpose is that ffmpeg is being used as a child subprocess and I would like to be able to test its behavior in-situ. There is a lot of timing in my application between fork and join and having ffmpeg be slow would be really helpful. Push comes to shove, I'll just use another program to more slowly copy, but that wouldn't be as good as using ffmpeg itself since it has a host of behaviors as a child process regarding signaling and return codes. Come to think of it, since I built ffmpeg, maybe I can just build a variant that sleeps frequently? Thanks for any clever ideas!

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Loading shared libraries in macOS
by Aleksid 12 Aug '20

12 Aug '20

Why is ffmpeg looking for shared libraries in a folder where I compiled FFmpeg sources on macOS Catalina? Source code of FFmpeg is located in /usr/local/Cellar/ffmpeg ./configure --enable-shared --extra-cflags="-fno-stack-check" --enable-gpl --enable-version3 --enable-pthreads --enable-nonfree make Then I put all compiled shared libraries and small ffmpeg binary file to a folder: /Users/aleks/test/ I call ./ffmpeg Library not loaded: /usr/local/Cellar/ffmpeg/lib/libavdevice.58.dylib Referenced from: /Users/aleks/test/./ffmpeg Reason: image not found Why? All shared libraries are located in the same folder as ffmpeg executable: /Users/aleks/test/

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Grid of videos starting at different times
by Randy Johnson 12 Aug '20

12 Aug '20

Hello, I have several videos that were recorded in a webinar type setting. Each person in the webinar was recorded with their own feed. I then receive a zip file with each video recording and a JSON file with a start / stop time offset. Example: Video 1: "filename" : "823ef68a-cb1c-4636-bdfb-ed3d9611a755.webm", "size" : 4766189, "startTimeOffset" : 17599, "stopTimeOffset" : 72696, Video 2: "filename" : "a920ab58-a42d-49fe-a239-b27497b22bb1.webm", "size" : 6378071, "startTimeOffset" : 1439, "stopTimeOffset" : 74655, I could have anywhere from 2 to 10 videos per job. For faster processing I convert the videos to Mp4 I have had some luck in merging the videos into 1 using hstack but I cannot seem to figure out how to get them merged into 1 video with the different time offsets. Here is what I have so far which gets me close but doesn't take into account the different offsets so everyone is talking over each other and out of order etc. ffmpeg -i /Users/randy/Downloads/archive23/a920ab58-a42d-49fe-a239-b27497b22bb1.mp4 -i /Users/randy/Downloads/archive23/823ef68a-cb1c-4636-bdfb-ed3d9611a755.mp4 -filter_complex \ "[0:v][1:v]hstack=inputs=2[v]; \ [0:a][1:a]amerge[a]" \ -map "[v]" -map "[a]" -ac 2 -y /Users/randy/Downloads/archive23/output.mp4 Another tricky thing is that if the conference was 1 hour long, someone could show up 15 minutes late or leave 15 minutes early. I thought ffmpeg -itsoffset n could be of help but https://stackoverflow.com/questions/55492772/stacking-different-length-vide… this post says that hstack doesn't sync with timestamps. They do give an example in the stack overflow post: ffmpeg \ -i smaller.mp4 \ -i bigger.mp4 \ -filter_complex \ "[0]tpad=start_duration=17[left];\ [left][1]hstack=inputs=2;\ [0]adelay=17s|17s[lefta];[lefta][1]amix=2" \ -c:v libx264 -crf 23 out.mp4 Any ideas on the best way for me to proceed? Thanks, Randy

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Negative segment durations in m3u8 file
by Valentin Schweitzer 11 Aug '20

11 Aug '20

Hi, when using the HLS muxer, some segment durations in the output m3u8 file are negative when specifying a very short hls_time. Using the attached 264 file and FFmpeg head, this behavior can be recreated like this: ./ffmpeg -report -i test.264 -pix_fmt yuv420p -vcodec libx264 -b:v 10000k -hls_segment_type fmp4 -hls_time 0.1 -hls_flags split_by_time+second_level_segment_index -strftime 1 -hls_segment_filename stream-%%18d.m4s -hls_playlist_type event index.m3u8 The command line output can be found in the attached log file. This command produces output along the lines of [...] #EXTINF:0.160000, stream-000000000000000108.m4s #EXTINF:-0.080000, stream-000000000000000109.m4s #EXTINF:0.200000, stream-000000000000000110.m4s #EXTINF:0.160000, stream-000000000000000111.m4s #EXTINF:-0.040000, stream-000000000000000112.m4s #EXTINF:0.200000, [...] An uncut example m3u8 file is attached. The varying output lengths are expected, due to splitting along I-Frames, although negative durations seems like an error. As I am not sure if this is a case of user error, I'd like to ask for any advice to fix this issue and, if possible, find out why it occurs before opening a trac ticket. The command above is a shortened version of the original command with which this bug was discovered. A change of framerate using -r 30 changes the output values, but still leaves some negative timestamps. This behaviour was tested on Ubuntu with FFmpeg HEAD and on Windows with the latest Zeranoe pre-built. I would be thankful for any advice. Greetings, Valentin

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MP4 concat filter with subtitles
by Gojko Adzic 11 Aug '20

11 Aug '20

Hi, Is there a way to concatenate multiple files while joining subtitles? I'm currently using the concat filter (need to re-encode the inputs) and naively tried to use concat=n=2:v=1:a=1:s=1, which failed as the concat filter doesn't seem to like the s output. thanks in advance! gojko

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Stream microphone to speakers
by Vi Rak 11 Aug '20

11 Aug '20

Dear gentle experts, I'm working on the Karaoke project for both Android and iOS where a user could record their performances (their video and vocal) and I use FFmpeg for mixing music with their recordings. Anyway, I wish I could route/pipe user vocal at realtime (capture thru device microphone) to an output device (speaker) so the user could hear their voice at realtime applied with some level of echo (to produce an effect as if we were in classic karaoke room). Over weeks I have been struggling with searching the ways to implement that based on FFmpeg, but no luck. Please kindly help. Many thanks in advance. Virak

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FFmpeg distribution help
by Don Fotheringham 09 Aug '20

09 Aug '20

Hello, We have developed software that requires the distribution of FFmpeg (included in the download). Our intention is to sell the software. Who do I contact to inquire further about how to proceed regarding permission, royalties, fees etc.? Thank you, Don Fotheringham

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WavPack to PCM?
by esikcalabrese＠verizon.net 09 Aug '20

09 Aug '20

Is there a way to convert WavPack format to PCM using ffmpeg? Kirk Calabrese, MA,CMT, Network+ Certified Professional IT Consultant

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