I have the following 3hour/12GB video that I'd like to compress further so it's about 1GB:
Container : MPEG-PS
Duration: 03:02:14.36, start: 0.226767, bitrate: 9463 kb/s
Stream #0:0[0x80]: Audio: ac3, 48000 Hz, 5.1(side), s16, 448 kb/s
Stream #0:1[0x1e0]: Video: mpeg2video (Main), yuv420p, 720x576 [SAR
64:45 DAR 16:9], 25 fps, 25 tbr, 90k tbn, 50 tbc
This when played in VLC has no sound/no video (Ffmpeg N-46469-gc995644):
Even this sample has no sound/no video:Code:ffmpeg -i input.mpg -ss 0 -t 30 -c:v libx264 -vf scale=iw/2:-1 -preset faster -c:a copy output.mpg
Does someone know of a no-brainer tool for Windows that could do the job?Code:ffmpeg -i input.mpg -ss 0 -t 30 -c:v copy -c:a copy output.sample.mpg
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Last edited by yetanotherlogin; 18th Nov 2012 at 08:11.
You couldn't create an iPod video to look good from 12GB to 1GB.
Thanks for the help. Quality is not an issue, as it's just a conference to show to people who couldn't be there.
ffmpeg -i input.mpg -c:v libx264 -vf scale=iw/2:-1 -preset faster -c:a copy output.mp4
Quality (in the video sense) may not be an issue but the end-user would still expect to be able to see it.
The 'container' is just that. It contains the compressed video. In your latest example you have a more efficient codec ie h264 rather than mpeg2 which you can not reasonably compress below 3-4000 kbps. You still end up with a 5-6 gb vid.
But do the full 3 hour vid. I am sure you still will struggle to get that down to 1 gb.
Halfway-through, the file is 400MB, so it should be about 800MB. Stay tuned for the quality check.
Edit: Works fine. Video is 360x288 25fps.
Last edited by yetanotherlogin; 18th Nov 2012 at 08:02.
There's no desync between audio/video and the definition is good enough for watching, considering it's just people in a conference.
Format : MPEG-4 Format profile : Base Media Codec ID : isom File size : 781 MiB Duration : 3h 2mn Overall bit rate : 599 Kbps Writing application : Lavf54.36.100 Video ID : 1 Format : AVC Format/Info : Advanced Video Codec Format profile : High@L2.1 Format settings, CABAC : Yes Format settings, ReFrames : 4 frames Codec ID : avc1 Codec ID/Info : Advanced Video Coding Duration : 3h 2mn Bit rate : 146 Kbps Width : 360 pixels Height : 288 pixels Display aspect ratio : 16:9 Frame rate mode : Constant Frame rate : 25.000 fps Color space : YUV Chroma subsampling : 4:2:0 Bit depth : 8 bits Scan type : Progressive Bits/(Pixel*Frame) : 0.056 Stream size : 190 MiB (24%) Writing library : x264 core 128 r2216 198a7ea Encoding settings : cabac=1 / ref=2 / deblock=1:0:0 / analyse=0x3:0x113 / me=hex / subme=4 / psy=1 / psy_rd=1.00:0.00 / mixed_ref=0 / me_range=16 / chroma_me=1 / trellis=1 / 8x8dct=1 / cqm=0 / deadzone=21,11 / fast_pskip=1 / chroma_qp_offset=0 / threads=3 / 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=1 / keyint=250 / keyint_min=25 / scenecut=40 / intra_refresh=0 / rc_lookahead=20 / rc=crf / mbtree=1 / crf=23.0 / qcomp=0.60 / qpmin=0 / qpmax=69 / qpstep=4 / ip_ratio=1.40 / aq=1:1.00 Audio ID : 2 Format : AC-3 Format/Info : Audio Coding 3 Mode extension : CM (complete main) Format settings, Endianness : Big Codec ID : ac-3 Duration : 3h 2mn Bit rate mode : Constant Bit rate : 448 Kbps Channel(s) : 6 channels Channel positions : Front: L C R, Side: L R, LFE Sampling rate : 48.0 KHz Bit depth : 16 bits Compression mode : Lossy Delay relative to video : -1s 24ms Stream size : 584 MiB (75%)
The video does indeed look respectable. Not brilliant and you would never get that at that bit-rate.
You have probably overdone it with the audio and that saved bit-rate could then be applied to the video.
Yup, I'll experiment with the audio and see how it goes. The reason I left it as is, is that a so-so video + good audio is watchable, while a good video with inaudible audio isn't.
I haven't reduced audio before, which is why I simply left "-c:a copy". Should I keep AAC and a lower bit-rate, or use eg. MP3?
You 're currently using AC3 , not AAC
AAC is more efficient type of audio compression than AC3 or MP3.
I would convert to stereo AAC. For speech, even 64kbps is more than enough, especially if you use AAC v2 (AAC-HE).
I don't know how to do that stereo conversion with ffmpeg syntax (also ffmpeg's choice of aac encoders are poor, neroaac and apple aac e.g. using qaac are better and consistently rate higher)
Thanks. BTW, is it possible to only keep some of the channels, so we only hear what's in front of the camcorder and not on the sides?
"Channel positions : Front: L C R, Side: L R, LFE"
5.1 from a camcorder won't be "real 5.1" - there will be crosstalk betwen channels
Yes, you can do a custom mix in an audio editor - something like audacity
"Normal" stereo downmixing filters have a ratio that incorporates all channels (because it's assumed the source 5.1 is real 6 discrete channels, eg. from a DVD or blu-ray with audio done in the studio)