An MP4 is a box of tracks. Lift out the sound.
Your video file already holds its audio as a separate track. Pick which one, trim it if you like, and we save it on its own: 97% smaller than the video it came from.
Open MP4, MKV, MOV, AVI, WMV, FLV, RealMedia, DVD VOB, camcorder MTS or almost anything else, and save it as any of 32 formats. The converting happens in this tab. Your video is never uploaded.
Each file is identified from its first bytes as soon as you add it. Once the engine is loaded it is read in full, so you see the real codecs, size and length before you convert.
MPEG-4 Part 14 on the ISO base media format. The safest choice when a file has to play anywhere.
ffmpeg -i input.mp4 -map 0:v:0 -map 0:a:0? -vf "scale=trunc(iw/2)*2:trunc(ih/2)*2" -c:v libx264 -preset veryfast -crf 23 -pix_fmt yuv420p -c:a aac -b:a 128k -ac 2 -f mp4 -movflags +faststart video.mp4Video needs millions of pixels every second; sound needs a few thousand samples. That's why dropping the picture shrinks a file so dramatically, and why the sharper the video, the bigger the saving.
Almost every MP4 stores its audio as AAC. Getting an MP3 means decoding that and compressing it again, a second round of loss. Keeping it as M4A just copies the original track out untouched.
Videos don't carry song titles or artists, so an extracted track shows up in music apps as its file name. Fill these in and they're written into the file (as ID3 tags for MP3, iTunes-style tags for M4A), so every player shows them.
Extracting audio is one of several ways to get a smaller, more useful file out of a video.