[Libav-user] Does the image2 demuxer work with a custom AVIOContext?

Robert Krüger krueger at lesspain.de
Fri Feb 21 13:22:26 CET 2014

On Fri, Feb 21, 2014 at 12:54 PM, Paul B Mahol <onemda at gmail.com> wrote:
> On 2/21/14, Robert Krueger <krueger at lesspain.de> wrote:
>> On Thu, Feb 20, 2014 at 3:01 PM, Paul B Mahol <onemda at gmail.com> wrote:
>>> On 2/20/14, Robert Krueger <krueger at lesspain.de> wrote:
>>>> On Wed, Feb 19, 2014 at 10:02 PM, Paul B Mahol <onemda at gmail.com> wrote:
>>>>> On 2/19/14, Carl Eugen Hoyos <cehoyos at ag.or.at> wrote:
>>>>>> Carl Eugen Hoyos <cehoyos at ...> writes:
>>>>>>> Robert Krueger <krueger <at> ...> writes:
>>>>>>> > cat ~/samples/fate/dpx/lighthouse_rgb48.dpx | ./ffmpeg
>>>>>>> > -f image2pipe -vcodec dpx -i - ~/tmp/fromdpx_pipe2.png
>>>>>>> > [dpx  <at>  0x7fcb21822600] Overread buffer. Invalid header?
>>>>>>> The image is cut in the middle
>>>>>> Iiuc, the parser reads the file size from the file
>>>>>> header while the decoder calculates the (minimal
>>>>>> possible) file size. The value that the parser
>>>>>> reads from the file header is too small.
>>>>>> I suspect the bug can be fixed by reusing the logic
>>>>>> to determine the image size also in the parser or
>>>>>> by ignoring the file size outputting everything until
>>>>>> the next magic marker.
>>>>> There is no bug in parser, bug is in dpx file which do not
>>>>> conform to the specification.
>>>>> FFmpeg dpx encoder is fine.
>>>>> ImageMagick sucks.
>>>> OK, I didn't know the file was generated using ImageMagick but I see
>>>> it now. Then it is irrelevant for me and I will ignore this as long as
>>>> valid dpx files work with this approach. Thank you for the analysis. I
>>>> don't know what the sample is used for in fate but maybe it's there
>>>> for testing broken dpx files. It just happend to be there when I was
>>>> looking for a dpx file to test the image2pipe approach.
>>> The sample is made before dpx encoder existed in ffmpeg....
>> OK, if it helps I could generate some dpx samples for fate using
>> Software like Adobe Speedgrade. Just let me know if there is interest
>> in that.
> Does such dpx files works with dpx parser?

I have only tried other samples from the software "Nuke" and those
worked. But I don't own these samples and I don't have that software.
I will make samples anyway and then I'll tell you if they work with
the parser and then you can decide whether you are interested in the

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