FFMPEG和PHP将视频转换为mp4和快照

Question

I have recently started working on a website where users can upload videos to, and I am a beginner with ffmpeg, however I have been searching and searching for how to do these things I want to do, however most of them aren't working for me.

I would like to convert any video type to .mp4 and keep the quality as good as possible. Right now my code is only working for .mov and .mp4 uploads, however .avi aren't converting (it doesn't even make a new file for those).

I would also like to take high quality screenshots from the video as well, but the screenshots I am getting now seem to be really low quality, so I don't know what's up with that.

The code I'm using now is this:

$ffmpeg = "/Users/USERNAME/ffmpeg/ffmpeg";
$src    = "/Applications/MAMP/htdocs/lounge/videos/".$filename."_original.".$ext;
$img    = "/Applications/MAMP/htdocs/lounge/videos/thumbnails/".$filename."_1.jpg";
$img2   = "/Applications/MAMP/htdocs/lounge/videos/thumbnails/".$filename."_2.jpg";
$img3   = "/Applications/MAMP/htdocs/lounge/videos/thumbnails/".$filename."_3.jpg";
$video  = "/Applications/MAMP/htdocs/lounge/videos/".$filename.".mp4";

$src = preg_replace("/ /", "\ ", $src);
$img = preg_replace("/ /", "\ ", $img);

$imgOutput  = shell_exec("$ffmpeg -ss 1 -i $src -s 960x540 -f image2 -vframes 1 $img");
$imgOutput2 = shell_exec("$ffmpeg -ss 15 -i $src -s 960x540 -f image2 -vframes 1 $img2");
$imgOutput3 = shell_exec("$ffmpeg -ss 30 -i $src -s 960x540 -f image2 -vframes 1 $img3");

$videoOuput = shell_exec("$ffmpeg -y -i $src 2>&1 -s vga $video");

How could I go about outputting 720p or 1080p videos?

Answer 1

FFMpeg is a very powerful solution, however you'll need to get used to its very numerous options to get what you want.

First of all, what you need is to identify what software/hardware will play your videos.

I will assume here that the videos are going to be played on a website probably using a flash player, or an HTML5 player (JWPlayer is both, for instance).

Then you need to find the best video and audio format for the quality you need. Please be aware that .mp4 is just a container, that can contain various video and audio formats. FFMpeg is smart enough to use by default AVC (H.264) for video, and AAC for audio, which is good, but probably will not give you perfect results, unless you specify the bitrate or quality you want.

Please read this extremely useful link http://ffmpeg.org/trac/ffmpeg/wiki/x264EncodingGuide before proceeding further.

You should probably use ABR or CBR mode if you want to ensure a predictible network throughput, or a CRF mode (18 to 20 will give you great quality) if you are concerned mainly about quality.

Resizing video is a complex topic by itself. You can find yourself being confronted to videos with a non-square Sample Aspect Ratio, meaning the video is meant to be watched in a size different from the actual width or height, or simply videos with a 4:3 ratio that you will try to resize to a 16:9 ratio, causing deformations.

Using the -s option actually inserts a scale filter which resize video frames using by default a bi-linear filtering algorithm. This is usually good enough for your needs, but it is sometimes more interesting to use a filter explicitly, if you are going to do other processing steps on the video. For example:

-vf "scale=-1:720"

This forces a height of 720 pixels, but ensures that the output ratio is the same as the input ratio, so the video will not be deformed.

Be aware that actually making a video bigger will not improve its quality anyways, will increase processing time, as well as the file size.

Finally, there is an issue that MUST be taken care of after an MP4 encoding for files that will be played via HTTP. MP4 files contain an atom called MOOV which is a block of data describing the contents of the file. A player software needs to read this block in order to be able to start playback, which is not an issue locally if the file is found on disk, but blocks file playing when downloaded from HTTP if it is found at the end of the file, because the WHOLE file must be downloaded before playback can start. Guess what, FFMpeg puts the MOOV atom at the end of the file, therefore it is not suited for HTTP progressive playback by default.

You must use a tool like qt-faststart or MP4Box to modify the file to place the MOOV atom at the beginning.

Answer 2

Have you tried -preset veryslow -qp 0 ? Read in SirDarius' suggested link as a preset for lossless H.264 best compression.