Hi,
i am trying to find the frame sizes (in bytes ) using decode_mpeg2.
Can i take the difference of
mpeg2_getpos() return values when it hits the STATE_PICTURE(when the picture
header is found) and STATE_SLICE(when the last slice of a picture has been
found) to get the exact frame size.
Thanks in advance
regards
anand
On 4/5/07, Keith Winstein <[EMAIL PROTECTED]> wrote:
Hi Anand,
Please reply to the list in case somebody else wants to chime in.
mpeg2_getpos() returns the total number of bytes (octets) since the start
of the stream. So yes, you will have to take the difference between
hitting one PICTURE header and the next header (probably PICTURE or
SEQUENCE) in order to find the coded length of the picture (in bytes).
There's basically no way to determine the coded length of the picture
until you hit the next header.
Best,
Keith
On Wed, 4 Apr 2007, anand meher wrote:
> Hi kieth,
> As i mentioned earlier i am looking for the frame
> sizes(i.ethe exact no of bytes ) required for coding,
> I am calling mpeg2_getpos() in STATE_PICTURE. of
decode_mpeg2
> function .I am getting an integer number in return.Can u please explain
> further to get the exact frame sizes . do we need to take the
> diference(i.ethe difference of the return value pf mpeg2_getpos()when
> 1st picture header
> was hit and the second return value from mpeg2_getpos() when the next
> picture header is hit.... OR
>
> will the reurn value of mpeg2_getpos() directly gives the frame size...?
> looking
> for ur reply and thanks in advance
>
> regards
>
> anand.
>
>
>
> i hope i am making sense..please correct me if i am wrong ) .
>
>
> On 4/4/07, anand meher < [EMAIL PROTECTED]> wrote:
>>
>> Hi keith,
>> i am glad to recieve a mail from you.I am working on a
>> project which requires the exact frame sizes(i.e the no of bytes)
>> required to code. I am using mpeg2dec.c program in libmpeg2 . There is
a
>> function called as decode_mpeg2 which is a kind of event handler.
>>
>> The point 1 in ur reply is the exact one i was asking about. I
>> think in the decode_mpeg2
>> function and in the case STATE_PICTURE ,we need to call
mpeg2_getpos().I
>> will try for that.
>> anyways i am really glad for ur quick reply.
>> If i get any more doubts..i will try
to
>> mail you.
>>
>> Thanks & regards
>>
>> Anand.
>>
>>
>>
>>
>> On 4/4/07, Keith Winstein < [EMAIL PROTECTED]> wrote:
>> >
>> > Hi Anand,
>> >
>> > Not sure exactly what you mean. Are you asking about:
>> >
>> > (1) The number of bits required to code each picture ( e.g., "911376
bits
>> > for the I frame, 115936 for the B frame after it, etc.")? For this,
>> > you'll
>> > have to call mpeg2_getpos() to get the position in the stream as you
hit
>> > PICTURE headers.
>> >
>> > (2) The horizontal and vertical sizes of the luma and chroma
matrices.
>> > These are in the sequence header -- see the code to dump_state.c for
an
>> > example. E.g., "1920x1088 for luma, 960x544 for chroma".
>> >
>> > (3) The intended displayed area of the frame (e.g., "1920x1080").
This
>> > is
>> > in the sequence display extension header, also printed out by
>> > dump_state.c
>> > ("seq->display_width", etc.).
>> >
>> > Sizes #2 and #3 are not allowed to vary on a picture-by-picture
basis.
>> > Only by ending the sequence and then starting a new sequence can you
>> > change the size of the image. (A picture display extension header can
>> > vary
>> > the location of the "display rectangle" within the full luma and
chroma
>> > matrices, but it can't change the dimensions of the "display
>> > rectangle.")
>> >
>> > Hope that helps. If you can be more specific I'd be happy to help
>> > further.
>> >
>> > Best,
>> > Keith
>> >
>> > On Wed, 4 Apr 2007, anand meher wrote:
>> >
>> > > Hi,
>> > > i am trying to find the frame sizes of the individual i,b,p
frame
>> > > sizes using libmpeg2.the current picture data structure does not
>> > provide
>> > > with the frame size.so is there any other way to find the frame
sizes
>> > > usiiiing libmpeg2. i am using the decode function in
mpeg2dec.cprogram
>> of
>> > > libmpeg2.
>> > >
>> > > thanks in advance
>> > >
>> >
>>
>>
>
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