Heatshrink compressed drives? - Tamp ISO compression test (Announce)
> I fail to see where the total number of
> sectors in the image is stored, though?
I didn't, as I thought the driver tested that, but turns out it just uses the file size. That would mean either moving the offsets to the end, adding a pointer to that, then testing EOF; or store the number of sectors and test it; or leave it and hope. :)
> I am curious about the distribution of compressed sector sizes for typical ISOs
As tom said (it doesn't matter what I have, it matters what you have). Having said that, I did another test with LZ4 and here's what I got.
LZ4 Tamp LZ4 gzip
Ratio % Ratio % Ratio % Ratio %
250GAMES 1.36 73.4 1.41 70.8 1.51 66.2 1.61 62.3
APC4101 1.03 97 1.03 96.9 1.05 95.4 1.06 94.7
EXTREME 1.49 67.2 1.68 59.6 1.8 55.6 2.09 47.9
fdosgame135b 1.69 59.3 1.81 55.1 2.01 49.7 2.25 44.4
FUZZYCD 1.18 84.8 1.22 81.9 1.43 70.2 1.45 69.1
Holmes2 1.13 88.2 1.19 83.7 1.3 76.7 1.42 70.5
NFSPCCD 1.12 89.6 1.14 87.7 1.16 85.8 1.24 80.4
osborne 1.62 61.6 1.7 58.7 1.94 51.6 2.11 47.5
PCU_OCT99_1 1.06 94.7 1.06 94.4 1.08 92.9 1.08 92.2
PCU_OCT99_2 1.01 99.2 1.01 99 1.01 98.5 1.02 98.2
PCW 1.29 77.7 1.44 69.5 1.55 64.3 1.77 56.5
RTZ-CD 1.1 91 1.15 86.7 1.33 75 1.44 69.5
Stellar7 1.08 92.8 1.13 88.3 1.14 87.4 1.3 76.7
Titus 1.13 88.1 1.16 86.3 1.2 83.6 1.24 80.8
APC, PCU & PCW are magazine cover discs; osborne is from my first PC (PC-DOS 6.3 & WfWg 3.11); the rest are games.
LZ4 (1.10.0) & Tamp are sector compression, the other LZ4 (1.3b) & gzip are file; ratio is the size of the original compared to the compressed (original_size / compressed_size); % is the opposite (compressed_size / original_size * 100).
Whilst LZ4 did save half a gig, and Tamp another 100 meg on top of that, I still don't think it's worth the effort.
> A simple scheme would be to only store the absolute offset of every 16th
> compressed sector, followed by only the 16 lower bits for the next 15
> offsets.
A less simple scheme that saves even more would be to store only the length, allowing packing two sectors into three bytes (a la FAT12); doing that for 32 sectors would be 52 bytes (dword address plus 48 bytes for the 32 lengths). Not sure how practical it would end up being, though.
Complete thread:
- lDebug release 9 - ecm, 21.12.2024, 13:49 (Announce)
- lDebug release 9 - Heatshrink compressed drives? - mceric, 21.12.2024, 16:00
- lDebug release 9 - Heatshrink compressed drives? - ecm, 21.12.2024, 18:41
- lDebug release 9 - Heatshrink compressed drives? - mceric, 21.12.2024, 22:55
- lDebug release 9 - Heatshrink compressed drives? - DosWorld, 02.01.2025, 18:24
- lDebug release 9 - Heatshrink compressed drives? - jadoxa, 29.01.2025, 08:46
- Heatshrink compressed drives? - Tamp ISO compression test - mceric, 30.01.2025, 02:21
- Heatshrink compressed drives? - Tamp ISO compression test - tom, 30.01.2025, 17:36
- Heatshrink compressed drives? - Tamp ISO compression test - jadoxa, 31.01.2025, 09:24
- Heatshrink compressed drives? - Tamp ISO compression test - mceric, 31.01.2025, 15:15
- Heatshrink compressed drives? - Tamp ISO compression test - mceric, 31.01.2025, 23:33
- Heatshrink compressed drives? - Tamp ISO compression test - tom, 01.02.2025, 11:19
- Heatshrink compressed drives? - Tamp ISO compression test - mceric, 01.02.2025, 13:54
- Heatshrink compressed drives? - Tamp ISO compression test - jadoxa, 01.02.2025, 15:33
- Heatshrink compressed drives? - Tamp ISO compression test - mceric, 01.02.2025, 13:54
- Heatshrink compressed drives? - Tamp ISO compression test - mceric, 06.02.2025, 02:42
- Snappy compression - ecm, 06.02.2025, 04:26
- Snappy compression - mceric, 08.02.2025, 01:04
- Snappy compression - script to build a compressed executable - ecm, 08.02.2025, 18:02
- Snappy compression - script to build a compressed executable - ecm, 09.02.2025, 21:38
- Snappy compression - script to build a compressed executable - ecm, 08.02.2025, 18:02
- Snappy compression - mceric, 08.02.2025, 01:04
- Snappy compression - ecm, 06.02.2025, 04:26
- Heatshrink compressed drives? - Tamp ISO compression test - tom, 01.02.2025, 11:19
- Heatshrink compressed drives? - Tamp ISO compression test - mceric, 31.01.2025, 23:33
- Heatshrink compressed drives? - Tamp ISO compression test - tom, 31.01.2025, 17:42
- Heatshrink compressed drives? - Tamp ISO compression test - mceric, 31.01.2025, 15:15
- lDebug release 9 - Heatshrink compressed drives? - Oso2k, 30.01.2025, 05:12
- Heatshrink compressed drives? - Tamp ISO compression test - mceric, 30.01.2025, 02:21
- lDebug release 9 - Heatshrink compressed drives? - ecm, 21.12.2024, 18:41
- lDebug release 9 - Heatshrink compressed drives? - mceric, 21.12.2024, 16:00