[libav-api] Resolution Change

Stefan Lederer ledererstefan at gmx.at
Sun Apr 24 14:24:07 CEST 2011

Hi Luca, 

thanks for your answer! 

I'm sorry, my explanation was not very clear. VLC actually does not crash,
it just does not decode the video correctly after the resolution changed
during the segmented MP4 and. I've added the libav output during this phase
after the resolution change to this email. 

I've created the segmented MP4 with mp4box, which offers some options for
this. The resolution change happens always at an IDR frame, is there
anything else I have to consider for this? Do I have to add some additional
boxes to the MP4 to signal the resolution change?

I've also provided some of the content which I used for this in [1]. There
are one initialization segment and two video segments in the attached

Thanks you for your help!!
Best Regards

[1] http://www.bitmovin.net/uni-klu/dash/foreman.zip 

On 4/24/11 10:15 AM, Stefan Lederer wrote:
> Hello,


> I'm developing adaptive dynamic http streaming over http (DASH) using 
> VLC for my master thesis at university. In this scenario I receive 
> segmented MP4 content which is downloaded via http . This content can 
> have different bitrates (which works quite well) and also different 
> resolution (that's the problem). My problem is that the VLC player 
> crashes when I switch from one resolution content (e.g. 720p) to 
> another resolution (e.g. 1080p) during playback. The problem occurs in 
> h264.c in the ff_h264_check_intra4x4_pred_mode function which the 
> error: top block unavailable for requested intra4x4 mode.

Could you please craft a minimal testcase using libav only? and/or provide a
full backtrace?

> How can I tell ffmpeg that the resolution of the content has changed 
> during playback? Is this even possible?

It seems working correctly with mpegts as container so I'm not sure yet
where the problem is.

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