Transcode WEBM to RTMP - ffmpeg

Question

Summary
My goal is to take a webcam stream from the browser and feed it into a program called Restreamer that takes in an RTMP stream.
I've deduced that the browser Recording API produces Blobs that can be saved as WEBM.
In order to stream the WEBM content to Restreamer I am attempting to use FFmpeg. I've read that forcing FLV format is required but otherwise all of the arguments are Greek to me. I've been unable to find a comparable topic where someone has tried to go from WEBM to RTMP. I have found examples of going the other direction, but reversing the FFmpeg command proved unfruitful.
Saving to FLV works fine. Using the following command, I am able to transcode a WEBM file to FLV and play it on VLC:
ffmpeg -i ~/big-buck-bunny_trailer.webm -f flv out.flv
However, if instead of outputting to a file I pass it to RTMP I get the following output:
ffmpeg -i ~/Downloads/big-buck-bunny_trailer.webm -f flv "rtmp://example.com/live"
ffmpeg version 5.0.1 Copyright (c) 2000-2022 the FFmpeg developers
built with gcc 12 (GCC)
configuration: --prefix=/usr --bindir=/usr/bin --datadir=/usr/share/ffmpeg --docdir=/usr/share/doc/ffmpeg --incdir=/usr/include/ffmpeg --libdir=/usr/lib64 --mandir=/usr/share/man --arch=x86_64 --optflags='-O2 -flto=auto -ffat-lto-objects -fexceptions -g -grecord-gcc-switches -pipe -Wall -Werror=format-security -Wp,-D_FORTIFY_SOURCE=2 -Wp,-D_GLIBCXX_ASSERTIONS -specs=/usr/lib/rpm/redhat/redhat-hardened-cc1 -fstack-protector-strong -specs=/usr/lib/rpm/redhat/redhat-annobin-cc1 -m64 -mtune=generic -fasynchronous-unwind-tables -fstack-clash-protection -fcf-protection' --extra-ldflags='-Wl,-z,relro -Wl,--as-needed -Wl,-z,now -specs=/usr/lib/rpm/redhat/redhat-hardened-ld -specs=/usr/lib/rpm/redhat/redhat-annobin-cc1 -Wl,--build-id=sha1 ' --extra-cflags=' -I/usr/include/rav1e' --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libvo-amrwbenc --enable-version3 --enable-bzlib --enable-chromaprint --disable-crystalhd --enable-fontconfig --enable-frei0r --enable-gcrypt --enable-gnutls --enable-ladspa --enable-libaom --enable-libdav1d --enable-libass --enable-libbluray --enable-libbs2b --enable-libcdio --enable-libdrm --enable-libjack --enable-libfreetype --enable-libfribidi --enable-libgsm --enable-libilbc --enable-libmp3lame --enable-libmysofa --enable-nvenc --enable-openal --enable-opencl --enable-opengl --enable-libopenjpeg --enable-libopenmpt --enable-libopus --enable-libpulse --enable-librsvg --enable-librav1e --enable-librtmp --enable-librubberband --enable-libsmbclient --enable-version3 --enable-libsnappy --enable-libsoxr --enable-libspeex --enable-libsrt --enable-libssh --enable-libsvtav1 --enable-libtesseract --enable-libtheora --enable-libtwolame --enable-libvorbis --enable-libv4l2 --enable-libvidstab --enable-libvmaf --enable-version3 --enable-vapoursynth --enable-libvpx --enable-vulkan --enable-libglslang --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxvid --enable-libxml2 --enable-libzimg --enable-libzmq --enable-libzvbi --enable-lv2 --enable-avfilter --enable-libmodplug --enable-postproc --enable-pthreads --disable-static --enable-shared --enable-gpl --disable-debug --disable-stripping --shlibdir=/usr/lib64 --enable-lto --enable-libmfx --enable-runtime-cpudetect
libavutil 57. 17.100 / 57. 17.100
libavcodec 59. 18.100 / 59. 18.100
libavformat 59. 16.100 / 59. 16.100
libavdevice 59. 4.100 / 59. 4.100
libavfilter 8. 24.100 / 8. 24.100
libswscale 6. 4.100 / 6. 4.100
libswresample 4. 3.100 / 4. 3.100
libpostproc 56. 3.100 / 56. 3.100
Input #0, matroska,webm, from '/home/kyjus25/big-buck-bunny_trailer.webm':
Metadata:
encoder : http://sourceforge.net/projects/yamka
creation_time : 2010-05-20T08:21:12.000000Z
Duration: 00:00:32.48, start: 0.000000, bitrate: 533 kb/s
Stream #0:0(eng): Video: vp8, yuv420p(progressive), 640x360, SAR 1:1 DAR 16:9, 25 fps, 25 tbr, 1k tbn (default)
Stream #0:1(eng): Audio: vorbis, 44100 Hz, mono, fltp (default)
HandShake: client signature does not match!
Stream mapping:
Stream #0:0 -> #0:0 (vp8 (native) -> flv1 (flv))
Stream #0:1 -> #0:1 (vorbis (native) -> mp3 (libmp3lame))
Press [q] to stop, [?] for help
Output #0, flv, to 'rtmp://example.com/live':
Metadata:
encoder : Lavf59.16.100
Stream #0:0(eng): Video: flv1 ([2][0][0][0] / 0x0002), yuv420p(tv, bt470bg/unknown/unknown, progressive), 640x360 [SAR 1:1 DAR 16:9], q=2-31, 200 kb/s, 25 fps, 1k tbn (default)
Metadata:
encoder : Lavc59.18.100 flv
Side data:
cpb: bitrate max/min/avg: 0/0/200000 buffer size: 0 vbv_delay: N/A
Stream #0:1(eng): Audio: mp3 ([2][0][0][0] / 0x0002), 44100 Hz, mono, fltp (default)
Metadata:
encoder : Lavc59.18.100 libmp3lame
WriteN, RTMP send error 32 (136 bytes)7kB time=00:00:00.39 bitrate= 136.7kbits/s speed=71.2x
WriteN, RTMP send error 32 (35 bytes)
WriteN, RTMP send error 9 (42 bytes)
av_interleaved_write_frame(): Operation not permitted
Last message repeated 1 times
[flv # 0x55d0dd0af700] Failed to update header with correct duration.
[flv # 0x55d0dd0af700] Failed to update header with correct filesize.
Error writing trailer of rtmp://example.com/live: Operation not permitted
frame= 53 fps=0.0 q=4.3 Lsize= 146kB time=00:00:02.45 bitrate= 486.8kbits/s speed=42.8x
video:128kB audio:19kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: unknown
Error closing file rtmp://example.com/live: Operation not permitted
Conversion failed!
There are several interesting rabbit holes to follow here, but after following all of them I've come up with nothing.
• HandShake: client signature does not match!:
More of a warning than an error, I assumed because I was going from "WEBM -> FLV" instead of the more traditional "MP4 -> FLV".
• av_interleaved_write_frame(): Operation not permitted:
I found several issues on this. One of them calling it a storage issue, the other calling it a file permissions issue. I have plenty of disk space and have tried setting the input file to 777 permissions. However, the examples I've found on it being a file permissions issue all deal with outputting to a file rather than to an an RTMP IP.
• Failed to update header with correct duration:
Advice I found was to add -flvflags no_duration_filesize to the command, which does suppress both "Failed to update..." errors, but does not fix the over-arching issue.
What I've Tried
• Multi-format transcoding
MP4 to RTMP does work correctly:
ffmpeg -i ~/Downloads/big-buck-bunny_trailer.mp4 -f flv "rtmp://example.com/live"
Theoretically, I could stream the WEBM to a file, transcode that to an MP4 file, and then transcode that to FLV/RTMP. Sounds awful.
• Pay for a service (Wowza, Flashphoner, api.video, etc)
Unfortunately precisely what I am trying to avoid.
• WebRTC to RTMP?
WebRTC seems to be a peer-to-peer connection and doesn't play nicely with a server/client scenario.
• WebRTC to other ingest formats
Restreamer also supports incoming streams of HLS, DASH, RTP, RTSP, RTMP, and SRT. However, these all seem to be examples of network sources that would be exposed via an IP URL. I am not sure that FFmpeg can do that.
• Utilizing ffmpeg-wasm instead of CLI
Available here, I thought that maybe by using a browser implementation I may get different results. But no. Not even an error to the console.
• Streaming from OBS
For the record, yes, I have tried streaming from OBS instead of going through FFmpeg and the Restreamer platform itself does work for normal use. I use it often.
Post Script
I've not been able to find any relevant solutions online. I am shocked that streaming from a browser webcam has not been solved 1000 times prior. This is related to a question made 7 years ago but it was not resolved and Flash is no longer an option.
Recommendations
• Adding -c:v libx264 -flags:v +global_header -c:a aac -ac 2:
ffmpeg version 5.0.1 Copyright (c) 2000-2022 the FFmpeg developers
built with gcc 12 (GCC)
configuration: --prefix=/usr --bindir=/usr/bin --datadir=/usr/share/ffmpeg --docdir=/usr/share/doc/ffmpeg --incdir=/usr/include/ffmpeg --libdir=/usr/lib64 --mandir=/usr/share/man --arch=x86_64 --optflags='-O2 -flto=auto -ffat-lto-objects -fexceptions -g -grecord-gcc-switches -pipe -Wall -Werror=format-security -Wp,-D_FORTIFY_SOURCE=2 -Wp,-D_GLIBCXX_ASSERTIONS -specs=/usr/lib/rpm/redhat/redhat-hardened-cc1 -fstack-protector-strong -specs=/usr/lib/rpm/redhat/redhat-annobin-cc1 -m64 -mtune=generic -fasynchronous-unwind-tables -fstack-clash-protection -fcf-protection' --extra-ldflags='-Wl,-z,relro -Wl,--as-needed -Wl,-z,now -specs=/usr/lib/rpm/redhat/redhat-hardened-ld -specs=/usr/lib/rpm/redhat/redhat-annobin-cc1 -Wl,--build-id=sha1 ' --extra-cflags=' -I/usr/include/rav1e' --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libvo-amrwbenc --enable-version3 --enable-bzlib --enable-chromaprint --disable-crystalhd --enable-fontconfig --enable-frei0r --enable-gcrypt --enable-gnutls --enable-ladspa --enable-libaom --enable-libdav1d --enable-libass --enable-libbluray --enable-libbs2b --enable-libcdio --enable-libdrm --enable-libjack --enable-libfreetype --enable-libfribidi --enable-libgsm --enable-libilbc --enable-libmp3lame --enable-libmysofa --enable-nvenc --enable-openal --enable-opencl --enable-opengl --enable-libopenjpeg --enable-libopenmpt --enable-libopus --enable-libpulse --enable-librsvg --enable-librav1e --enable-librtmp --enable-librubberband --enable-libsmbclient --enable-version3 --enable-libsnappy --enable-libsoxr --enable-libspeex --enable-libsrt --enable-libssh --enable-libsvtav1 --enable-libtesseract --enable-libtheora --enable-libtwolame --enable-libvorbis --enable-libv4l2 --enable-libvidstab --enable-libvmaf --enable-version3 --enable-vapoursynth --enable-libvpx --enable-vulkan --enable-libglslang --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxvid --enable-libxml2 --enable-libzimg --enable-libzmq --enable-libzvbi --enable-lv2 --enable-avfilter --enable-libmodplug --enable-postproc --enable-pthreads --disable-static --enable-shared --enable-gpl --disable-debug --disable-stripping --shlibdir=/usr/lib64 --enable-lto --enable-libmfx --enable-runtime-cpudetect
libavutil 57. 17.100 / 57. 17.100
libavcodec 59. 18.100 / 59. 18.100
libavformat 59. 16.100 / 59. 16.100
libavdevice 59. 4.100 / 59. 4.100
libavfilter 8. 24.100 / 8. 24.100
libswscale 6. 4.100 / 6. 4.100
libswresample 4. 3.100 / 4. 3.100
libpostproc 56. 3.100 / 56. 3.100
Input #0, matroska,webm, from '/home/kyjus25/big-buck-bunny_trailer.webm':
Metadata:
encoder : http://sourceforge.net/projects/yamka
creation_time : 2010-05-20T08:21:12.000000Z
Duration: 00:00:32.48, start: 0.000000, bitrate: 533 kb/s
Stream #0:0(eng): Video: vp8, yuv420p(progressive), 640x360, SAR 1:1 DAR 16:9, 25 fps, 25 tbr, 1k tbn (default)
Stream #0:1(eng): Audio: vorbis, 44100 Hz, mono, fltp (default)
HandShake: client signature does not match!
Stream mapping:
Stream #0:0 -> #0:0 (vp8 (native) -> h264 (libx264))
Stream #0:1 -> #0:1 (vorbis (native) -> aac (native))
Press [q] to stop, [?] for help
[libx264 # 0x561564271fc0] using SAR=1/1
[libx264 # 0x561564271fc0] using cpu capabilities: MMX2 SSE2Fast SSSE3 SSE4.2 AVX FMA3 BMI2 AVX2
[libx264 # 0x561564271fc0] profile High, level 3.0, 4:2:0, 8-bit
[libx264 # 0x561564271fc0] 264 - core 163 r3060 5db6aa6 - H.264/MPEG-4 AVC codec - Copyleft 2003-2021 - http://www.videolan.org/x264.html - options: cabac=1 ref=3 deblock=1:0:0 analyse=0x3:0x113 me=hex subme=7 psy=1 psy_rd=1.00:0.00 mixed_ref=1 me_range=16 chroma_me=1 trellis=1 8x8dct=1 cqm=0 deadzone=21,11 fast_pskip=1 chroma_qp_offset=-2 threads=11 lookahead_threads=1 sliced_threads=0 nr=0 decimate=1 interlaced=0 bluray_compat=0 constrained_intra=0 bframes=3 b_pyramid=2 b_adapt=1 b_bias=0 direct=1 weightb=1 open_gop=0 weightp=2 keyint=250 keyint_min=25 scenecut=40 intra_refresh=0 rc_lookahead=40 rc=crf mbtree=1 crf=23.0 qcomp=0.60 qpmin=0 qpmax=69 qpstep=4 ip_ratio=1.40 aq=1:1.00
Output #0, flv, to 'rtmp://example.com/live':
Metadata:
encoder : Lavf59.16.100
Stream #0:0(eng): Video: h264 ([7][0][0][0] / 0x0007), yuv420p(tv, bt470bg/unknown/unknown, progressive), 640x360 [SAR 1:1 DAR 16:9], q=2-31, 25 fps, 1k tbn (default)
Metadata:
encoder : Lavc59.18.100 libx264
Side data:
cpb: bitrate max/min/avg: 0/0/0 buffer size: 0 vbv_delay: N/A
Stream #0:1(eng): Audio: aac (LC) ([10][0][0][0] / 0x000A), 44100 Hz, stereo, fltp, 128 kb/s (default)
Metadata:
encoder : Lavc59.18.100 aac
Larger timestamp than 24-bit: 0xffffff77kB time=00:00:30.18 bitrate= 460.0kbits/s speed=19.7x
[flv # 0x56156425e440] Failed to update header with correct duration.
[flv # 0x56156425e440] Failed to update header with correct filesize.
frame= 812 fps=475 q=-1.0 Lsize= 1901kB time=00:00:32.52 bitrate= 479.0kbits/s speed= 19x
video:1354kB audio:508kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 2.123872%
[libx264 # 0x561564271fc0] frame I:21 Avg QP:15.05 size: 8839
[libx264 # 0x561564271fc0] frame P:293 Avg QP:20.78 size: 3087
[libx264 # 0x561564271fc0] frame B:498 Avg QP:22.20 size: 593
[libx264 # 0x561564271fc0] consecutive B-frames: 14.7% 7.6% 9.2% 68.5%
[libx264 # 0x561564271fc0] mb I I16..4: 42.6% 41.9% 15.5%
[libx264 # 0x561564271fc0] mb P I16..4: 4.0% 8.0% 0.9% P16..4: 22.7% 8.0% 4.0% 0.0% 0.0% skip:52.4%
[libx264 # 0x561564271fc0] mb B I16..4: 1.4% 1.5% 0.2% B16..8: 12.0% 1.0% 0.2% direct: 3.3% skip:80.5% L0:44.1% L1:47.1% BI: 8.8%
[libx264 # 0x561564271fc0] 8x8 transform intra:53.6% inter:57.0%
[libx264 # 0x561564271fc0] coded y,uvDC,uvAC intra: 35.1% 37.7% 11.2% inter: 7.8% 9.5% 2.4%
[libx264 # 0x561564271fc0] i16 v,h,dc,p: 56% 21% 14% 9%
[libx264 # 0x561564271fc0] i8 v,h,dc,ddl,ddr,vr,hd,vl,hu: 32% 26% 21% 3% 3% 4% 4% 3% 4%
[libx264 # 0x561564271fc0] i4 v,h,dc,ddl,ddr,vr,hd,vl,hu: 27% 21% 18% 4% 7% 7% 6% 5% 4%
[libx264 # 0x561564271fc0] i8c dc,h,v,p: 62% 21% 15% 2%
[libx264 # 0x561564271fc0] Weighted P-Frames: Y:20.8% UV:19.5%
[libx264 # 0x561564271fc0] ref P L0: 70.3% 17.7% 9.0% 2.9% 0.0%
[libx264 # 0x561564271fc0] ref B L0: 89.3% 8.9% 1.9%
[libx264 # 0x561564271fc0] ref B L1: 96.4% 3.6%
[libx264 # 0x561564271fc0] kb/s:341.30
[aac # 0x561564223140] Qavg: 952.636
Seems to complete successfully, but does so rather quickly. Log outputs a new Larger timestamp than 24-bit: 0xffffff77kB

Answer 1

Was able to get it to work by using:
ffmpeg -re -i sample.webm -c:v h264 -c:a aac -f flv "rtmp://example.com/live"
The -re was essential to make it stream in real time, otherwise #Gyan's suggestion would have also worked!