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I'm trying to add the ability to compress video files in my project. However, I tried to extract the Audio from the original video file using FFMPEG Library before compressing it. The command line was
-i video.mp4 -c:a aac -b:a 160k target.m4a
After the encoding was done I noticed that the output is still a video file but with a difference in the size. This brought two questions to me and I would like to know their answers.
1 - can the ".m4a" file be considered as a video file?
2 - can I use this command line to compress video files?
Best regards
Log after executing the command
<p>
success load
started encoding
ffmpeg version n3.0.1 Copyright (c) 2000-2016 the FFmpeg developers
built with gcc 4.8 (GCC)
configuration: --target-os=linux --cross-prefix=/home/vagrant/SourceCode/ffmpeg-android/toolchain-android/bin/arm-linux-androideabi- --arch=arm --cpu=cortex-a8 --enable-runtime-cpudetect --sysroot=/home/vagrant/SourceCode/ffmpeg-android/toolchain-android/sysroot --enable-pic --enable-libx264 --enable-libass --enable-libfreetype --enable-libfribidi --enable-libmp3lame --enable-fontconfig --enable-pthreads --disable-debug --disable-ffserver --enable-version3 --enable-hardcoded-tables --disable-ffplay --disable-ffprobe --enable-gpl --enable-yasm --disable-doc --disable-shared --enable-static --pkg-config=/home/vagrant/SourceCode/ffmpeg-android/ffmpeg-pkg-config --prefix=/home/vagrant/SourceCode/ffmpeg-android/build/armeabi-v7a --extra-cflags='-I/home/vagrant/SourceCode/ffmpeg-android/toolchain-android/include -U_FORTIFY_SOURCE -D_FORTIFY_SOURCE=2 -fno-strict-overflow -fstack-protector-all' --extra-ldflags='-L/home/vagrant/SourceCode/ffmpeg-android/toolchain-android/lib -Wl,-z,relro -Wl,-z,now -pie' --extra-libs='-lpng -lexpat -lm' --extra-cxxflags=
libavutil 55. 17.103 / 55. 17.103
libavcodec 57. 24.102 / 57. 24.102
libavformat 57. 25.100 / 57. 25.100
libavdevice 57. 0.101 / 57. 0.101
libavfilter 6. 31.100 / 6. 31.100
libswscale 4. 0.100 / 4. 0.100
libswresample 2. 0.101 / 2. 0.101
libpostproc 54. 0.100 / 54. 0.100
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from '/storage/emulated/0/tempVid.mp4':
Metadata:
major_brand : 3gp4
minor_version : 0
compatible_brands: isom3gp4
creation_time : 2017-11-30 03:22:41
com.android.version: 6.0.1
Duration: 00:00:19.80, start: 0.000000, bitrate: 4246 kb/s
Stream #0:0(eng): Video: h264 (Baseline) (avc1 / 0x31637661), yuv420p, 176x144, 4112 kb/s, SAR 1:1 DAR 11:9, 29.94 fps, 29.97 tbr, 90k tbn, 180k tbc (default)
Metadata:
rotate : 270
creation_time : 2017-11-30 03:22:41
handler_name : VideoHandle
Side data:
displaymatrix: rotation of 90.00 degrees
Stream #0:1(eng): Audio: amr_nb (samr / 0x726D6173), 8000 Hz, mono, flt, 12 kb/s (default)
Metadata:
creation_time : 2017-11-30 03:22:41
handler_name : SoundHandle
[libx264 @ 0xb5bc4400] using SAR=1/1
[libx264 @ 0xb5bc4400] using cpu capabilities: none!
[libx264 @ 0xb5bc4400] profile High, level 1.1
[libx264 @ 0xb5bc4400] 264 - core 148 - H.264/MPEG-4 AVC codec - Copyleft 2003-2015 - 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=5 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
[aac @ 0xb5bc4c00] Too many bits 20480.000000 > 6144 per frame requested, clamping to max
Output #0, ipod, to '/storage/emulated/0/target.m4a':
Metadata:
major_brand : 3gp4
minor_version : 0
compatible_brands: isom3gp4
com.android.version: 6.0.1
encoder : Lavf57.25.100
Stream #0:0(eng): Video: h264 (libx264) (avc1 / 0x31637661), yuv420p, 144x176 [SAR 1:1 DAR 9:11], q=-1--1, 29.97 fps, 30k tbn, 29.97 tbc (default)
Metadata:
handler_name : VideoHandle
creation_time : 2017-11-30 03:22:41
encoder : Lavc57.24.102 libx264
Side data:
unknown side data type 10 (24 bytes)
Stream #0:1(eng): Audio: aac (LC) (mp4a / 0x6134706D), 8000 Hz, mono, fltp, 48 kb/s (default)
Metadata:
creation_time : 2017-11-30 03:22:41
handler_name : SoundHandle
encoder : Lavc57.24.102 aac
Stream mapping:
Stream #0:0 -> #0:0 (h264 (native) -> h264 (libx264))
Stream #0:1 -> #0:1 (amr_nb (amrnb) -> aac (native))
Press [q] to stop, [?] for help
frame= 47 fps=0.0 q=0.0 size= 0kB time=00:00:00.76 bitrate= 0.5kbits/s speed=1.53x
frame= 69 fps= 68 q=29.0 size= 12kB time=00:00:01.79 bitrate= 56.3kbits/s speed=1.77x
frame= 88 fps= 57 q=29.0 size= 22kB time=00:00:02.30 bitrate= 76.5kbits/s speed=1.49x
frame= 110 fps= 54 q=29.0 size= 31kB time=00:00:02.81 bitrate= 89.9kbits/s speed=1.37x
frame= 118 fps= 45 q=29.0 size= 34kB time=00:00:03.84 bitrate= 71.5kbits/s speed=1.47x
frame= 144 fps= 46 q=29.0 size= 44kB time=00:00:03.84 bitrate= 93.7kbits/s speed=1.23x
frame= 150 fps= 41 q=29.0 size= 48kB time=00:00:04.86 bitrate= 80.6kbits/s speed=1.34x
frame= 178 fps= 42 q=29.0 size= 62kB time=00:00:04.86 bitrate= 105.2kbits/s speed=1.16x
frame= 185 fps= 39 q=29.0 size= 67kB time=00:00:05.88 bitrate= 93.4kbits/s speed=1.25x
frame= 206 fps= 40 q=29.0 size= 78kB time=00:00:05.88 bitrate= 108.5kbits/s speed=1.13x
frame= 214 fps= 37 q=29.0 size= 84kB time=00:00:06.91 bitrate= 99.8kbits/s speed=1.21x
frame= 238 fps= 38 q=29.0 size= 100kB time=00:00:06.91 bitrate= 118.0kbits/s speed=1.11x
frame= 249 fps= 37 q=29.0 size= 106kB time=00:00:07.93 bitrate= 109.3kbits/s speed=1.18x
frame= 268 fps= 37 q=29.0 size= 119kB time=00:00:08.19 bitrate= 119.1kbits/s speed=1.13x
frame= 279 fps= 36 q=29.0 size= 127kB time=00:00:08.96 bitrate= 116.4kbits/s speed=1.16x
frame= 298 fps= 36 q=29.0 size= 140kB time=00:00:09.21 bitrate= 124.4kbits/s speed=1.11x
frame= 308 fps= 35 q=29.0 size= 149kB time=00:00:09.98 bitrate= 122.3kbits/s speed=1.14x
frame= 328 fps= 35 q=29.0 size= 162kB time=00:00:10.24 bitrate= 129.5kbits/s speed= 1.1x
frame= 343 fps= 35 q=29.0 size= 172kB time=00:00:10.88 bitrate= 129.2kbits/s speed=1.11x
frame= 358 fps= 35 q=29.0 size= 180kB time=00:00:11.90 bitrate= 124.0kbits/s speed=1.15x
frame= 387 fps= 36 q=29.0 size= 195kB time=00:00:11.90 bitrate= 134.1kbits/s speed=1.09x
frame= 398 fps= 35 q=29.0 size= 202kB time=00:00:12.92 bitrate= 127.9kbits/s speed=1.14x
frame= 418 fps= 35 q=29.0 size= 213kB time=00:00:13.31 bitrate= 131.3kbits/s speed=1.12x
frame= 432 fps= 35 q=29.0 size= 222kB time=00:00:13.95 bitrate= 130.3kbits/s speed=1.13x
frame= 448 fps= 35 q=29.0 size= 230kB time=00:00:14.59 bitrate= 129.0kbits/s speed=1.13x
frame= 469 fps= 35 q=29.0 size= 242kB time=00:00:14.97 bitrate= 132.5kbits/s speed=1.11x
frame= 478 fps= 34 q=29.0 size= 247kB time=00:00:15.87 bitrate= 127.6kbits/s speed=1.14x
frame= 509 fps= 35 q=29.0 size= 259kB time=00:00:16.00 bitrate= 132.8kbits/s dup=1 drop=0 speed=1.11x
frame= 525 fps= 35 q=29.0 size= 266kB time=00:00:17.02 bitrate= 127.8kbits/s dup=1 drop=0 speed=1.13x
frame= 539 fps= 35 q=29.0 size= 271kB time=00:00:17.79 bitrate= 124.5kbits/s dup=1 drop=0 speed=1.15x
frame= 564 fps= 35 q=29.0 size= 285kB time=00:00:18.04 bitrate= 129.4kbits/s dup=1 drop=0 speed=1.13x
frame= 574 fps= 35 q=29.0 size= 290kB time=00:00:19.07 bitrate= 124.8kbits/s dup=1 drop=0 speed=1.15x
frame= 590 fps= 35 q=29.0 size= 297kB time=00:00:19.45 bitrate= 125.2kbits/s dup=1 drop=0 speed=1.14x
frame= 594 fps= 33 q=-1.0 Lsize= 328kB time=00:00:19.84 bitrate= 135.2kbits/s dup=1 drop=0 speed= 1.1x
video:246kB audio:70kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 3.381132%
[libx264 @ 0xb5bc4400] frame I:3 Avg QP:22.61 size: 4103
[libx264 @ 0xb5bc4400] frame P:230 Avg QP:25.04 size: 851
[libx264 @ 0xb5bc4400] frame B:361 Avg QP:28.82 size: 121
[libx264 @ 0xb5bc4400] consecutive B-frames: 1.2% 40.7% 37.9% 20.2%
[libx264 @ 0xb5bc4400] mb I I16..4: 4.0% 49.8% 46.1%
[libx264 @ 0xb5bc4400] mb P I16..4: 0.1% 0.3% 0.2% P16..4: 52.0% 27.1% 15.1% 0.0% 0.0% skip: 5.3%
[libx264 @ 0xb5bc4400] mb B I16..4: 0.0% 0.0% 0.0% B16..8: 43.4% 2.1% 0.3% direct: 1.7% skip:52.5% L0:39.3% L1:55.4% BI: 5.3%
[libx264 @ 0xb5bc4400] 8x8 transform intra:51.7% inter:57.7%
[libx264 @ 0xb5bc4400] coded y,uvDC,uvAC intra: 81.9% 93.5% 80.4% inter: 11.9% 40.0% 17.4%
[libx264 @ 0xb5bc4400] i16 v,h,dc,p: 11% 25% 7% 57%
[libx264 @ 0xb5bc4400] i8 v,h,dc,ddl,ddr,vr,hd,vl,hu: 7% 20% 16% 6% 11% 5% 20% 6% 9%
[libx264 @ 0xb5bc4400] i4 v,h,dc,ddl,ddr,vr,hd,vl,hu: 11% 22% 14% 5% 10% 7% 19% 5% 7%
[libx264 @ 0xb5bc4400] i8c dc,h,v,p: 61% 18% 10% 10%
[libx264 @ 0xb5bc4400] Weighted P-Frames: Y:24.3% UV:22.2%
[libx264 @ 0xb5bc4400] ref P L0: 57.6% 14.3% 16.8% 8.9% 2.3%
[libx264 @ 0xb5bc4400] ref B L0: 76.3% 19.1% 4.6%
[libx264 @ 0xb5bc4400] ref B L1: 91.9% 8.1%
[libx264 @ 0xb5bc4400] kb/s:101.58
[aac @ 0xb5bc4c00] Qavg: 64130.668
success ffmpeg
end encoding
ffmpeg version n3.0.1 Copyright (c) 2000-2016 the FFmpeg developers
built with gcc 4.8 (GCC)
configuration: --target-os=linux --cross-prefix=/home/vagrant/SourceCode/ffmpeg-android/toolchain-android/bin/arm-linux-androideabi- --arch=arm --cpu=cortex-a8 --enable-runtime-cpudetect --sysroot=/home/vagrant/SourceCode/ffmpeg-android/toolchain-android/sysroot --enable-pic --enable-libx264 --enable-libass --enable-libfreetype --enable-libfribidi --enable-libmp3lame --enable-fontconfig --enable-pthreads --disable-debug --disable-ffserver --enable-version3 --enable-hardcoded-tables --disable-ffplay --disable-ffprobe --enable-gpl --enable-yasm --disable-doc --disable-shared --enable-static --pkg-config=/home/vagrant/SourceCode/ffmpeg-android/ffmpeg-pkg-config --prefix=/home/vagrant/SourceCode/ffmpeg-android/build/armeabi-v7a --extra-cflags='-I/home/vagrant/SourceCode/ffmpeg-android/toolchain-android/include -U_FORTIFY_SOURCE -D_FORTIFY_SOURCE=2 -fno-strict-overflow -fstack-protector-all' --extra-ldflags='-L/home/vagrant/SourceCode/ffmpeg-android/toolchain-android/lib -Wl,-z,relro -Wl,-z,now -pie' --extra-libs='-lpng -lexpat -lm' --extra-cxxflags=
libavutil 55. 17.103 / 55. 17.103
libavcodec 57. 24.102 / 57. 24.102
libavformat 57. 25.100 / 57. 25.100
libavdevice 57. 0.101 / 57. 0.101
libavfilter 6. 31.100 / 6. 31.100
libswscale 4. 0.100 / 4. 0.100
libswresample 2. 0.101 / 2. 0.101
libpostproc 54. 0.100 / 54. 0.100
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from '/storage/emulated/0/tempVid.mp4':
Metadata:
major_brand : 3gp4
minor_version : 0
compatible_brands: isom3gp4
creation_time : 2017-11-30 03:22:41
com.android.version: 6.0.1
Duration: 00:00:19.80, start: 0.000000, bitrate: 4246 kb/s
Stream #0:0(eng): Video: h264 (Baseline) (avc1 / 0x31637661), yuv420p, 176x144, 4112 kb/s, SAR 1:1 DAR 11:9, 29.94 fps, 29.97 tbr, 90k tbn, 180k tbc (default)
Metadata:
rotate : 270
creation_time : 2017-11-30 03:22:41
handler_name : VideoHandle
Side data:
displaymatrix: rotation of 90.00 degrees
Stream #0:1(eng): Audio: amr_nb (samr / 0x726D6173), 8000 Hz, mono, flt, 12 kb/s (default)
Metadata:
creation_time : 2017-11-30 03:22:41
handler_name : SoundHandle
[libx264 @ 0xb5bc4400] using SAR=1/1
[libx264 @ 0xb5bc4400] using cpu capabilities: none!
[libx264 @ 0xb5bc4400] profile High, level 1.1
[libx264 @ 0xb5bc4400] 264 - core 148 - H.264/MPEG-4 AVC codec - Copyleft 2003-2015 - 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=5 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
[aac @ 0xb5bc4c00] Too many bits 20480.000000 > 6144 per frame requested, clamping to max
Output #0, ipod, to '/storage/emulated/0/target.m4a':
Metadata:
major_brand : 3gp4
minor_version : 0
compatible_brands: isom3gp4
com.android.version: 6.0.1
encoder : Lavf57.25.100
Stream #0:0(eng): Video: h264 (libx264) (avc1 / 0x31637661), yuv420p, 144x176 [SAR 1:1 DAR 9:11], q=-1--1, 29.97 fps, 30k tbn, 29.97 tbc (default)
Metadata:
handler_name : VideoHandle
creation_time : 2017-11-30 03:22:41
encoder : Lavc57.24.102 libx264
Side data:
unknown side data type 10 (24 bytes)
Stream #0:1(eng): Audio: aac (LC) (mp4a / 0x6134706D), 8000 Hz, mono, fltp, 48 kb/s (default)
Metadata:
creation_time : 2017-11-30 03:22:41
handler_name : SoundHandle
encoder : Lavc57.24.102 aac
Stream mapping:
Stream #0:0 -> #0:0 (h26
</p>
520
asked Dec 20 '25 15:12
1 - can the ".m4a" file be considered as a video file?
Yes. If your input contained video then your output will too, because by default ffmpeg will automatically choose one stream per stream type from the input to map to the output.
As for the extension .m4a is intended to be used for audio files but I doubt it is functionally different than .m4v and .mp4.
2 - can I use this command line to compress video files?
Yes, and in fact your command did compress the video as well as the audio.
If you want to extract the audio you'll need to tell ffmpeg which streams you want and to tell it to stream copy (re-mux) without re-encoding. To include only the audio stream(s):
ffmpeg -i input.mp4 -map 0:a -c copy output.m4a
Or to exclude video:
ffmpeg -i input.mp4 -vn -c copy output.m4a
I prefer -map because it is more flexible; I almost never use -vn, -an, -sn, or -dn.
124
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