[FFmpeg-user] systematically encoding using x264
amit at sdsc.edu
Thu Dec 5 22:42:45 CET 2013
Thanks for this info. I am familiar with most of the options you provided.
All image sequences are at same resolution and format. So I dont have to worry about rescaling.
I am highly interested in identifying common sets of presets to create videos that will play on most devices.
Is there any guidance on common resolutions and bitrates for encoding videos playable on most devices?
As I understand the resolution and bitrates primarily govern requirements for various hardware profiles for *264 encoder.
Are there any processes with which one can achieve higher quality output complying with restrictions imposed by hardware profiles ?
lowering frame rate and two pass encoding come to my mind.
On Nov 29, 2013, at 5:14 AM, Frank Tetzel wrote:
>> I am looking for specific guidelines to encode many sequences of
>> image to a video using x264 encoder. The image resolution and frame
>> rate could be arbitrary (some sequences are 256x256 others could be
>> 4kx4k or more), usually with images 1:1 aspect ratio. I would like to
>> create multiple resolution/bitrate videos from these sequences which
>> could be served on multiple devices as well as downloaded. The
>> encoding time is not a very big concern but quality is a huge
>> concern, as these sequences have scientific content.
>> I am seeking some pointers on this and if there is someone out there
>> who may be interested in collaborating that will be great. I'll be
>> willing to open a set of sequences which could be used for tests,
>> benchmarks, quality comparisons etc.
> so you want to create slideshows with different quality settings
> including different resolutions?
> This page describes how to create slideshows:
> more information about the image format:
> "The size, the pixel format, and the format of each image must be the
> same for all the files in the sequence."
> If that's not the case you have to convert the images beforehand, e.g.
> with imagemagick.
> The scale video filter is described here:
> An example could be:
> ffmpeg -r 1/5 -i img%03d.png \
> -vf 'scale=256:-1' \
> -c:v libx264 -preset veryslow -tune stillimage -r 30 out.mp4
> As you want to append sequences with different framerates, you need to
> concatenate them. Something like that:
> ffmpeg -r 1/5 -i first/%03d.png -r 1/10 -i second/%03d.png \
> -filter_complex '[0:v] scale=256:-1 [v1]; \
> [1:v] scale=256:-1 [v2]; [v1][v2] concat, fps=30' out.mp4
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