[MEncoder-users] How important are B-frames?

[Sylvester]

On 5 May 2012 09:39, James Hastings-Trew <jimht at shaw.ca> wrote:
> On 12-05-03 9:23 PM, Sylvester 4 wrote:
>>
>> How important are B-frames and does a video really need them?
>>
>> "MEncoder's libavformat muxing is presently broken and can generate
>> INCORRECT files in the presence of B-frames. Moreover, due to bugs MPlayer
>> will play these INCORRECT files as if nothing were wrong!"
>>
>> If I encode using -of lavf, the above is displayed.  So, I would set
>> bframes=0 thinking this must be the correct procedure.  But I am now
>> wondering if a video is suffering in quality due to zero B-frames in
>> the video.
>>
>> Also, in MPEG-2 files, I notice they have - 99% of the time - BVOP.  I
>> think I remember it stands for bidirectional video object plane.  Is
>> this just another name for B-frames?
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> B-frames allow for a greater amount of compression because they represent a
> diff from both following frames and previous frames, in both temporal
> directions. Therefore they are not essential, and basically for years I used
> mencoder to create mp4 files with zero b-frames with no ill visual effect.
> Just slightly larger files. I should also note that some devices with very
> small frame buffers cannot handle video streams with b-frames correctly
> anyway - the original appleTV comes to mind, as well as many portable
> devices. The presence of b-frames requires buffering x-number of frames
> because b-frames can be delivered out of stream order and must be buffered
> at playback time.
>
> _______________________________________________

Thanks for your information on this.

Yes, I am encoding via x264 to AVC mp4.  Initially, I had B-frames set
to 3 and everything worked fine while playing via MPlayer.  Later on,
I noticed other players would show the video in a jerky, flicking way
as though frames were missing.  This was very apparent if a scene had
the camera panning from left to right or right to left slowly.  Awful.
 Setting it to 0 fix it.  For my use, I don't care if it is slightly
larger.