Since 2016-07-13, it's possible to encode VP9/webm videos with alpha channel (VP9a). You only need a copy of ffmpeg compiled after that date. By the way, all you need to write is: ffmpeg -i frames/%03d.png output.webm FFmpeg understands png format and will set a default framerate of 25 fps and a yuva420p pixel format to the output. Aug 5, 2011 · On Windows 7 I had to use the power shell (Start > Accessories > Windows Power Shell > Power Shell) and provide the full location for ffmpeg, input and output. Note the parameter -vcodec libvpx uses VP8 by default. To use VP9 replace with -vcodec libvpx-vp9. WedmbSD AV1 is an open source & royalty-free video codec developed by the Alliance for Open Media (AOMedia), a non-profit industry consortium. Depending on the use case, AV1 can achieve about 30% higher compression efficiency than VP9, and about 50% higher efficiency than H.264. There are currently three AV1 encoders supported by FFmpeg: libaom ... 5. I believe I found a solution: ffmpeg -hwaccel auto -i in.mp4 -c:v h264_nvenc -preset llhq -rc constqp -qp 21 -c:a copy out.mp4. It seems that h264_nvenc uses -qp instead of -crf. This option only works while -rc is set to constqp. Share. Improve this answer. Follow. answered Jan 26, 2018 at 18:50.What you need is sws_scale functionality of ffmpeg. This does two things, scaling and format conversion, both can be performed same time. Check scaling_video.c example. I have a downscaled frame already for both h264 and vp9 to encode and would like to get the advantage of VP9's which having a smaller size but maintain similar quality as h264.FFmpeg supports following functionality accelerated by video hardware on NVIDIA GPUs: Hardware-accelerated decoding of H.264, HEVC, VP9, VP8, MPEG2, MPEG4*, and AV1. Granular control over encoding settings such as encoding preset, rate control and other video quality parameters. Create high-performance end-to-end hardware-accelerated video ... Jul 28, 2017 · libvpx is the VP8 video encoder for WebM, an open, royalty-free media file format. This guide is an attempt to summarize the most important options for creating video with libvpx. To install FFmpeg with support for libvpx, look at the Compilation Guides and compile FFmpeg with the --enable-libvpx option. Note: The VP8 successor VP9 provides ... I want to use vp9 encoder to encode video with alpha channel (argb -> webm, through ffmpeg) in real time (less than 30ms/frame), but I found that even if the -deadline realtime -speed 8 parameter is added, the speed is improved Still not obvious.My command is: ffmpeg -framerate 30 -f image2 -i frames/%04d.png -i my_audio.flac -c:v libvpx-vp9 -pix_fmt yuva420p -b:v... Stack Exchange Network Stack Exchange network consists of 183 Q&A communities including Stack Overflow , the largest, most trusted online community for developers to learn, share their knowledge, and build their careers.May 28, 2018 · 1. What the VPx codecs in ffmpeg do is use the video bitrate value as a ceiling. If not set by the user, ffmpeg assumes a default of 200 kbps. You need to reset the value to get unconstrained CRF encoding. ffmpeg -y -i in.mkv -threads 6 -c:a libopus -c:v libvpx-vp9 -crf 30 -b:v 0 out.mkv. When I try to encode a video file with a two pass in ffmpeg, the output file of the first pass is empty using vp9. Hence I can not proceed with the second part. Code for the two-pass: 1.pass: ffmpeg -y -s:v 3840x1920 -framerate 30 -i video_framerate_resolution.yuv -c:v libvpx-vp9 -crf 20 -pass 1 -an -f avi NULL && \ 2.pass3. VP9 does not have a pure raw bitstream format. The closest thing is the lightweight IVF format - 32 byte global header + 12 byte header per frame . Use. ffmpeg -i input.webm -c copy stream.ivf. Share. Improve this answer. Follow.Nov 16, 2022 · Contents. libvpx-vp9 is the VP9 video encoder for WebM, an open, royalty-free media file format. libvpx-vp9 can save about 20–50% bitrate compared to libx264 (the default H.264 encoder), while retaining the same visual quality. To install FFmpeg with support for libvpx-vp9, look at the Compilation Guides and compile FFmpeg with the --enable ... Nov 14, 2013 · But with ffmpeg qmax may have different meaning as it's a codec dependent parameters. for x264 it should be a quantizer see here, But with some others codecs it doesn't represent a quantization level but a quality range. qmax and qmin are the 'quality-ranges' in which you define to encode. Oposite from what most, atleast me, would expect is ... Stack Exchange network consists of 183 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers.4. Libvpx has no hardware encoding or acceleration support of any kind, it's purely a software implementation. There are some VP9 hardware encoders out there but they're few in number and neither Nvidia or AMD have one. However, if you have an Intel CPU from the Skylake architecture or newer you should be able to use Intel's QuickSync hardware ...AV1 is an open source & royalty-free video codec developed by the Alliance for Open Media (AOMedia), a non-profit industry consortium. Depending on the use case, AV1 can achieve about 30% higher compression efficiency than VP9, and about 50% higher efficiency than H.264. There are currently three AV1 encoders supported by FFmpeg: libaom ...对于基于 VP9 的基于 H/W 的编码，我仍然强烈建议使用vp9_vaapi编码器包装器，并带有警告（与使用 B 帧和速率控制模式有关）。VAAPI 总体上比 QSV 更稳定。 参考： 查看编码器选项，包括支持的速率控制方法： ffmpeg -h encoder=vp9_qsv 关于vpp_qsv过滤器的使用，请参见：Use both -deadline and -cpu-used to control speed. -deadline has 3 modes: best, good, and rt. The -cpu-used option can tweak each mode to further adjust speed. The meaning/value of -cpu-used depends on the mode. best - This usually gives the best quality output but is extremely slow.Apr 23, 2019 · Pay attention to the output from the console: [AVHWDeviceContext @ 0x556f744cf5c0] VAAPI driver: Intel i965 driver for Intel(R) Skylake - 2.1.0. As you can see clock rate in input stream is 1/90000 (tbn 90k) , but in output 1/1000 (tbn 1k). How can I set a clock rate to 90k in output stream? Thanks a lot for help. EDIT I accept answer, because it is fact. But I solved my problem replacing webm container in -f parameter with rtp - and clock rate is 90k (tbn)VP9 decoder consists of libvpx and ffvp9 (developed). Generally, it will adopt libvpx for VP9 decoding as default. If you have FFmpeg installed on Windows 10, you can utilize ffvp9 for VP9 decoding, which ffvp9 trounces libvpx by 25-50% in decoding speed on a bounty of machines. Moreover, WinX Video Converter is an optimum selection.artiume • 3 yr. ago. Honestly you could just rename the file and no one would bat an eye. With ffmpeg though, ffmpeg -i input.webm -c:av copy output.mkv. 4. themisfit610 • 3 yr. ago. Don’t forget -c copy in the middle to avoid a transcode. 2. artiume • 3 yr. ago.This setup with that command encodes at ~126 fps. This compares to about 10 fps using libvpx-vp9 encoder! Using the global_quality of 70 for hardware encoding the file is about 60% bigger than an encoding using libvpx-vp9 at a crf of 32. I would say these settings give about the same quality degradation compared to the source.See FFmpeg Wiki: VP9. Using a lossless encoder. Assuming you want VP9 output: ffmpeg -i input.mp4 -vf "scale=-2:1080" -c:v libvpx-vp9 -lossless 1 -c:a copy output.webm This will make a huge sized file. See FFmpeg Wiki: VP9. Use a player. This will use a player named ffplay to downscale while playing. No output file is created.For the documentation of the undocumented generic options, see the Codec Options chapter . To get more documentation of the libvpx options, invoke the command ffmpeg -h encoder=libvpx, ffmpeg -h encoder=libvpx-vp9 or vpxenc --help. Further information is available in the libvpx API documentation. b (target-bitrate)ffmpeg -i video.webm -i audio.opus -c:v copy -c:a aac -strict experimental output.mp4. it should look something like this. ffmpeg -i audio.opus -i vid.webm -c:v copy -c:a opus -strict experimental output6.webm. replace aac with opus and the two files around with opus being in front (i think), it should work. Share.Last Modified: 2016-05-18 Examples given are for 2-pass VP9 encoding with FFMpeg. Ensure that your FFMpeg has been built with libvpx support. VOD Recommended Settings ffmpeg -i <source> -c:v libvpx-vp9 -pass 1 -b:v 1000K -threads 8 -speed 4 \ -tile-columns 6 -frame-parallel 1 \ -an -f webm /dev/nullSee FFmpeg Wiki: VP9. Using a lossless encoder. Assuming you want VP9 output: ffmpeg -i input.mp4 -vf "scale=-2:1080" -c:v libvpx-vp9 -lossless 1 -c:a copy output.webm This will make a huge sized file. See FFmpeg Wiki: VP9. Use a player. This will use a player named ffplay to downscale while playing. No output file is created.Jul 12, 2023 · ffmpeg -y -hwaccel_output_format d3d11 -hwaccel d3d11va -i input.mp4 -c:v hevc_nvenc out.mp4 NVDEC/CUVID. NVDEC offers decoders for H.264, HEVC, MJPEG, MPEG-1/2/4, VP8/VP9, VC-1, AV1. Codec support varies by hardware (see the GPU compatibility table). Note that FFmpeg offers both NVDEC and CUVID hwaccels. They differ in how frames are decoded ... 2. I'm trying to encode a sequence of 32-bit 8bpc PNG images (RGB with an alpha channel) using the lossless VP9 codec with ffmpeg; specifically: ffmpeg -framerate 60 -i out%04d.png -c:v libvpx-vp9 -lossless 1 -pix_fmt yuva420p output.webm. This seems to encode the video losslessly; however, when I run: ffmpeg -i output.webm out%04d.png.artiume • 3 yr. ago. Honestly you could just rename the file and no one would bat an eye. With ffmpeg though, ffmpeg -i input.webm -c:av copy output.mkv. 4. themisfit610 • 3 yr. ago. Don’t forget -c copy in the middle to avoid a transcode. 2. artiume • 3 yr. ago.ffmpeg -i output.mp4 -vcodec libvpx-vp9 -strict experimental output_2.webm ffmpeg -i output_2.webm -strict 2 output_3.mp4 This happens only with some youtube videos, not all of them. Is there a way to download all youtube videos in a readable format with only one command line, without having to convert to webm?libvpx-vp9 is the VP9 video encoder for WebM, an open, royalty-free media file format. libvpx-vp9 can save about 20–50% bitrate compared to libx264 (the default H.264 encoder), while retaining the same visual quality. To install FFmpeg with support for libvpx-vp9, look at the Compilation Guides and compile FFmpeg with the --enable-libvpx option.Jun 5, 2017 · ffmpeg -i input.mp4 -c:v vp9 -c:a libvorbis output.mkv. This will make a Matroska container with a VP9 video stream and a Vorbis audio stream, essentially the same as the WebM we made earlier. The command ffmpeg -codecs will print every codec FFmpeg knows about. The output of this command will change depending on the version of FFmpeg you have ... You should use VP9, it's slower, but the quality gain is worth it. There is not a lot of gain to tweak each options, you'll have really good results with ffmpeg -i in.mp4 -c:v libvpx-vp9 -crf 30 -b:v 0 -c:a libopus -b:a 64k -vbr on out.webm-crf is the quality level, the lower the betterWhen I try to encode a video file with a two pass in ffmpeg, the output file of the first pass is empty using vp9. Hence I can not proceed with the second part. Code for the two-pass: 1.pass: ffmpeg -y -s:v 3840x1920 -framerate 30 -i video_framerate_resolution.yuv -c:v libvpx-vp9 -crf 20 -pass 1 -an -f avi NULL && \ 2.passI find vp9 at a nominal 400k bit rate works great on 1280x720 video. (ffmpeg with libvpx-vp9 overshoots, and I typically end up with a 20% higher actual bit rate, 480k) 4K is 3840x2160, 9x the size of 1280x720, so it would seem a 3600k bit rate should produce good results. Another guide is that vp9 is reportedly about equal in quality to mp4 at ...Recently I found out that on some intel hardware pc, you can use hardware acceleration to encode videos that makes it a lot faster. So it doesn't take over 30 minutes to encode a 10 minute video at 3.2 fps. According to what I learned my pc uses a supported intel chip that supports encoding VP9 format. But I don't know how to do it, and it has ... Recently I found out that on some intel hardware pc, you can use hardware acceleration to encode videos that makes it a lot faster. So it doesn't take over 30 minutes to encode a 10 minute video at 3.2 fps. According to what I learned my pc uses a supported intel chip that supports encoding VP9 format. But I don't know how to do it, and it has ... Jun 5, 2017 · ffmpeg -i input.mp4 -c:v vp9 -c:a libvorbis output.mkv. This will make a Matroska container with a VP9 video stream and a Vorbis audio stream, essentially the same as the WebM we made earlier. The command ffmpeg -codecs will print every codec FFmpeg knows about. The output of this command will change depending on the version of FFmpeg you have ... FFmpeg, as of time of writing, does not support resolution-changes mid-stream while encoding. There is a patchset to introduce this ability. motivated for raw video and VP8/9 encoders, but it stands abandoned. Vlc Media Player from videolan.org can convert vp9 to h264. Under the Media menu, choose Convert/Save.libvpx-vp9 is the VP9 video encoder for WebM, an open, royalty-free media file format. libvpx-vp9 can save about 20–50% bitrate compared to libx264 (the default H.264 encoder), while retaining the same visual quality. To install FFmpeg with support for libvpx-vp9, look at the Compilation Guides and compile FFmpeg with the --enable-libvpx option.Additionally to the previously mentioned arguments, ffmpeg VP9 and H265 codecs accept -crf flag . It enables constant quality mode, which guarantees a certain perceptual quality level within the entire video by passing a number from 0-63(VP9) and 0-51(H265), where 0 is the best quality and the maximum number is the worst.I'm trying to transcode a webm using VP9 to VP8 for use in the Unity Game Engine. I'm using this command but the resulting video losses the alpha channel: ffmpeg -i myvideo.webm -c:v libvpx -pix_fmt yuva420p -metadata:s:v:0 alpha_mode="1" -acodec libvorbis converted.webm. I even tried to extract the PNGs but they also show without alpha!3 Answers Sorted by: 6 Basically ffmpeg supports VP9 encoding and decoding. It looks like your build of libvpx doesn't support VP9. For VP9 support you must use the experimental branch: $ git clone -b experimental http://git.chromium.org/webm/libvpx.git $ cd libvpx $ ./configure --enable-vp9 --enable-shared $ make && make installThe speed/quality options for VP8/VP9 are explained in the documentation. Note that in ffmpeg, you have to specify the parameters differently (see ffmpeg -h encoder=libvpx-vp9 ): CPU Usage: ffmpeg: -cpu-used (legacy option: -speed) libvpx: --cpu-usedRe-mux WebM to MP4. If you want to stream copy (re-mux) and avoid re-encoding: ffmpeg -i input.webm -c copy output.mp4. This will copy the VP9/VP8 video and Opus/Vorbis audio from WebM to MP4. This is like a "copy and paste". No re-encoding occurs, so no quality is lost and the process is very fast.【まとめ特集記事】 ビデオカード * VDPAU / VA-API * ffmpeg; H.264 vs H.265 vs VP8 vs VP9 vs AV1; キーボード頂上決戦! 東プレ RealForce R2 vs 富士通コンポーネント Libertouch vs Unicomp Ultra Classic 106JP; おすすめ記事. Pandoc Markdown のあまり知られていない書法Sep 19, 2020 · Use both -deadline and -cpu-used to control speed. -deadline has 3 modes: best, good, and rt. The -cpu-used option can tweak each mode to further adjust speed. The meaning/value of -cpu-used depends on the mode. best - This usually gives the best quality output but is extremely slow. Mar 19, 2021 · I have a WebM file with one video stream that was encoded with VP9 (libvpx-vp9). I wrote a C++ program to extract the frames from the video stream and save them out as PNG's. This works fine except that the resulting PNG's are missing alpha. If I extract the frames from the same WebM file using FFMPEG the resulting PNG's do contain alpha. Apr 6, 2017 · I find vp9 at a nominal 400k bit rate works great on 1280x720 video. (ffmpeg with libvpx-vp9 overshoots, and I typically end up with a 20% higher actual bit rate, 480k) 4K is 3840x2160, 9x the size of 1280x720, so it would seem a 3600k bit rate should produce good results. Another guide is that vp9 is reportedly about equal in quality to mp4 at ... Choosing the Right Command String Isolating the Key Differences Table 1: These results show that the CRF setting in the Google command string had little impact on output quality. Use a Speed Setting of 2 Boosting Encoding Speed with Row-MT Table 2: Adding row-mt cut encoding time by ~36% and boosted VMAF quality slightly.My command is: ffmpeg -framerate 30 -f image2 -i frames/%04d.png -i my_audio.flac -c:v libvpx-vp9 -pix_fmt yuva420p -b:v... Stack Exchange Network Stack Exchange network consists of 183 Q&A communities including Stack Overflow , the largest, most trusted online community for developers to learn, share their knowledge, and build their careers.FFmpeg doesn't have a stable built-in AAC encoder, so this command will just copy the audio stream in the same format to the output file. If VLC still doesn't like the audio codec, you can change the copy in -c:a copy to some other codec listed here. ffmpeg -i <input file> -c:a copy -c:v libx264 <output file>. FFmpeg should automatically detect ...Additionally to the previously mentioned arguments, ffmpeg VP9 and H265 codecs accept -crf flag . It enables constant quality mode, which guarantees a certain perceptual quality level within the entire video by passing a number from 0-63(VP9) and 0-51(H265), where 0 is the best quality and the maximum number is the worst.What you need is sws_scale functionality of ffmpeg. This does two things, scaling and format conversion, both can be performed same time. Check scaling_video.c example. I have a downscaled frame already for both h264 and vp9 to encode and would like to get the advantage of VP9's which having a smaller size but maintain similar quality as h264.Jun 30, 2017 · I want to re-encode a stream from an IP camera to WebM (VP8 or VP9) format with ffmpeg. I need real time speed, but my CPU is a Core i5 (2017) and too busy (load avarage too more 100%). Can I buy hardware that is better suited for such an encoding task? What parametres for ffmpeg are recommended for transcoding in realtime? Note: FFmpeg must be compiled with the --enable-libvpx option for VP9 to work. Most pre-compiled versions include this option by default. If your version of FFmpeg does not create VP9, it may be missing this compilation option. FFmpeg is a command-line program. Once you have it installed, you can perform encodes from the command line.FFmpeg, as of time of writing, does not support resolution-changes mid-stream while encoding. There is a patchset to introduce this ability. motivated for raw video and VP8/9 encoders, but it stands abandoned. Vlc Media Player from videolan.org can convert vp9 to h264. Under the Media menu, choose Convert/Save.It seems that the ffmpeg -quality command is the same as the -deadline command. These commands do not directly affect the other options, but merely determine the amount of time the encoder is allowed to spend on any particular frame. As commented in the vpx_encoder.h file in the libvpx code: The encoder supports the notion of a soft real-time ...Sep 19, 2020 · Use both -deadline and -cpu-used to control speed. -deadline has 3 modes: best, good, and rt. The -cpu-used option can tweak each mode to further adjust speed. The meaning/value of -cpu-used depends on the mode. best - This usually gives the best quality output but is extremely slow. 5. I believe I found a solution: ffmpeg -hwaccel auto -i in.mp4 -c:v h264_nvenc -preset llhq -rc constqp -qp 21 -c:a copy out.mp4. It seems that h264_nvenc uses -qp instead of -crf. This option only works while -rc is set to constqp. Share. Improve this answer. Follow. answered Jan 26, 2018 at 18:50.May 26, 2015 · It seems that the ffmpeg -quality command is the same as the -deadline command. These commands do not directly affect the other options, but merely determine the amount of time the encoder is allowed to spend on any particular frame. As commented in the vpx_encoder.h file in the libvpx code: The encoder supports the notion of a soft real-time ... You should use VP9, it's slower, but the quality gain is worth it. There is not a lot of gain to tweak each options, you'll have really good results with ffmpeg -i in.mp4 -c:v libvpx-vp9 -crf 30 -b:v 0 -c:a libopus -b:a 64k -vbr on out.webm-crf is the quality level, the lower the betterMay 25, 2023 · FFmpeg command-line settings to enable VP9 Profile 2 and HDR EOTFs. Your FFmpeg will need to have been built with 10-bit (or even 12-bit) support. In the examples below we use a statically-built ffmpeg with 10-bit support. You may use our build script to make your own, or follow the guidance on the FFmpeg site. Use both -deadline and -cpu-used to control speed. -deadline has 3 modes: best, good, and rt. The -cpu-used option can tweak each mode to further adjust speed. The meaning/value of -cpu-used depends on the mode. best - This usually gives the best quality output but is extremely slow.Oct 15, 2019 · FFMPEG encoder supports encoding with VP9 alpha transparency. Using the libvpx-vp9 encoder, creating a video is as easy as this: ffmpeg -framerate 60 -i frame_%05d.tif -pix_fmt yuva420p -an output.webm. There’s only a few things to note here. I’m setting the framerate to 60 frames per second. AV1 is an open source & royalty-free video codec developed by the Alliance for Open Media (AOMedia), a non-profit industry consortium. Depending on the use case, AV1 can achieve about 30% higher compression efficiency than VP9, and about 50% higher efficiency than H.264. There are currently three AV1 encoders supported by FFmpeg: libaom ... Aug 26, 2021 · I want to use vp9 encoder to encode video with alpha channel (argb -> webm, through ffmpeg) in real time (less than 30ms/frame), but I found that even if the -deadline realtime -speed 8 parameter is added, the speed is improved Still not obvious. The -lossless 1 option of ffmpeg’s VP9 encoder enables lossless quality mode, but with a potentially enormous increase in filesize. All you need is this: ffmpeg -i input.mp4 -lossless 1 output.webm. When I tried -lossless 1 on a low-quality mp4, the resulting webm was 100× larger, which was not accceptable to me. VP9 is an open and royalty-free [1] video coding format developed by Google . VP9 is the successor to VP8 and competes mainly with MPEG's High Efficiency Video Coding (HEVC/H.265). At first, VP9 was mainly used on Google's video platform YouTube. [2] [3] The emergence of the Alliance for Open Media, and its support for the ongoing development ... Feb 4, 2015 · ffmpeg -i video.webm -i audio.opus -c:v copy -c:a aac -strict experimental output.mp4. it should look something like this. ffmpeg -i audio.opus -i vid.webm -c:v copy -c:a opus -strict experimental output6.webm. replace aac with opus and the two files around with opus being in front (i think), it should work. Share. ffmpeg v4.0.2 or higher can encode/transcode VP9 in mp4. Commandline (when transcoding): ffmpeg -i INPUT.MKV -c:v libvpx-vp9 OUTPUT.MP4. Commandline (when remuxing (Super fast)): ffmpeg -i INPUT.MKV -c:v copy OUTPUT.MP4. Your second command isn't transcoding, it's called remuxing, the process of moving encoded streams from one container to ...Jul 20, 2021 · I'm trying to use ffmpeg to encode VP9 using vp9_qsv on windows 10. My CPU supports QuickSync (i7 11700k). ffmpeg -i output.mp4 -vcodec libvpx-vp9 -strict experimental output_2.webm ffmpeg -i output_2.webm -strict 2 output_3.mp4 This happens only with some youtube videos, not all of them. Is there a way to download all youtube videos in a readable format with only one command line, without having to convert to webm?. c:v libvpx-vp9 tells FFmpeg to encode the video in VP9. c:a libopusMay 25, 2023 · A variety of encoding products and cloud servi Jun 5, 2017 · ffmpeg -i input.mp4 -c:v vp9 -c:a libvorbis output.mkv. This will make a Matroska container with a VP9 video stream and a Vorbis audio stream, essentially the same as the WebM we made earlier. The command ffmpeg -codecs will print every codec FFmpeg knows about. The output of this command will change depending on the version of FFmpeg you have ... May 25, 2023 · FFmpeg command-line settings to enable VP9 Profile 2 and HDR EOTFs. Your FFmpeg will need to have been built with 10-bit (or even 12-bit) support. In the examples below we use a statically-built ffmpeg with 10-bit support. You may use our build script to make your own, or follow the guidance on the FFmpeg site. 2. I'm trying to encode a sequence of 32-bit 8bpc PNG images (RGB Aug 4, 2023 · ffmpeg -hwaccel qsv -c:v h264_qsv -i input.mp4 -f null - HEVC 10bit video decode and download as p010le yuv file ffmpeg -hwaccel qsv -c:v hevc_qsv -load_plugin hevc_hw -i input.mp4 -vf hwdownload,format=p010 -pix_fmt p010le output.yuv Encode-only. Check supported qsv encoder list ffmpeg -encoders|grep qsv Check private option list of h264 encoder ffmpeg -i file-with-vp9-video-and-opus-audio.webm -f ...
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