[FFmpeg-user] Encoding multiple files for adaptive bit rate streaming using RTMP and HLS

Henk D. Schoneveld belcampo at zonnet.nl
Tue May 12 16:32:17 CEST 2015

On 12 May 2015, at 15:50, Werner Robitza <werner.robitza at gmail.com> wrote:

> On Tue, May 12, 2015 at 3:16 PM, Henk D. Schoneveld <belcampo at zonnet.nl> wrote:
>>> On 12 May 2015, at 13:50, Werner Robitza <werner.robitza at gmail.com> wrote:
>>> On Tue, May 12, 2015 at 11:47 AM, Henk D. Schoneveld <belcampo at zonnet.nl> wrote:
>>>> Would you be so kind to explain why to NOT use the crf option?
>>> CRF is essentially a constant quality mode, which results in variable
>>> bitrate depending on the spatiotemporal complexity of the scenes.
>> Your goal is max quality within a given link-capacity I assume.
>> Upfront choosing an arbitrary bitrate to achieve max possible quality seems sub-optimal/contradictionary to me.
>> A. to many bits for talking heads
>> B. to few bits for action dominant events.
> Yes, but that's still what's typically done, unless you choose a CQ
> encoding type with a max-rate (which is what libvpx recommends too).
But libvpx is much less efficient than libx264 for the same quality.
> You should've mentioned that you're experienced with this -- otherwise
> I would've given a different answer.
Hm what difference does it make if I know a little bit more or less to how/what you’re answering ?
Another option to ‘optimise’ quality for a given bitrate is to use anamorphic encoding. I know YouTube doesn’t accept that but all modern players I know of handle it without any problem.
For 720p I use -s 880x720 which works for me pretty well. With this you’ll get a reduction of (1280-880)/1280=31% in needed bits for very reasonable quality. At least a lot better then reducing the bitrate by that % and using 1:1 ie. -s 1280x720 encoding.
>> I see the difference between the methods, but I don’t really understand what it’s trying to tel me. What does the X-axis say, total stream-size/#frames/ ?
> It's the frame number (index) in a 3 minute sequence.
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