Re: [Discuss-gnuradio] Streaming IQ File Compression

[Dave NotTelling]

Chris,

     Excellent, then I will start benchmarking tomorrow :)

Thanks!

On Sat, Jul 16, 2016 at 9:35 PM, Chris Kuethe <address@hidden> wrote:

Flac doesn't really need to know what the actual sample rate is; you
could tell it 500e3 and you should get the same data out after
compressing and decompressing it.

On Sat, Jul 16, 2016 at 11:20 AM, Dave NotTelling <address@hidden> wrote:
> Marcus & Dan,
>
>      Thank you very, very much for the detailed information!
>
> Dan: That's exactly what I thought when going into this at first.  But, I
> decided to give gzip a shot just to see how well it did.  Turns out that (at
> least for bursty environments) it almost halves the size of the original
> file.  It should be noted that the file was in fc32 format so there were
> likely a lot of unused bits there (or so I guess).
>
> Marcus: I have been giving thought to truncating some of the bits.  Going as
> far as thinking about dropping from sc16 to sc8.  I have worked with 8 bit
> sample files before and had plenty of success demodulating, so I'm thinking
> that it might be an okay path to go down.  Dynamic range goes to hell, but
> it it's worked in the past...  I think that re-packing as 12 bit would give
> considerable space savings without a lot of CPU overhead.  I'll have to give
> that one a go :)  I really like your idea of using FLAC.  Just a quick
> Google search netted http://www.rtl-sdr.com/compressing-filtering-iq-data/.
> What concerns me is that when I tried to use the command line flac in Ubuntu
> it said that the sample rate must be between 1 and 655349 Hz.  I'll have to
> poke around at it to see what happens when I set an incorrect bit rate
> (maybe a multiple of will be fine?).
>
> Thank you both!
>
> -Dave
>
> On Sat, Jul 16, 2016 at 5:14 AM, Marcus Müller <address@hidden>
> wrote:
>>
>> Ah!
>>
>> On 16.07.2016 11:04, Marcus Müller wrote:
>> > and maybe, but this is really speculation, you can just modify the
>> > error calculation to just ignore the 4 lower bits of the actual sample
>> > data, and safe another few percents of data volume.
>> Yeah, there's a FLAC__stream_encoder_set_bits_per_sample[0] function--
>> guess that you don't need to modify anything. Also, there's a whole
>> listing of things .._set_compression_level[1] sets internally. This
>> approach (using FLAC as lossless waveform encoder) might be really
>> interesting.
>>
>>
>>
>> [0]
>>
>> https://xiph.org/flac/api/group__flac__stream__encoder.html#gabfa3c989377785cda7c496b69dcb98cb
>> [1]
>>
>> https://xiph.org/flac/api/group__flac__stream__encoder.html#ga07fc8c7806381a055a1eef26387e509f
>>
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GDB has a 'break' feature; why doesn't it have 'fix' too?