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ED-ME-5 1-DVD
11 octobre 2011, par
Mis à jour : Octobre 2011
Langue : English
Type : Audio
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Revolution of Open-source and film making towards open film making
6 octobre 2011, par
Mis à jour : Juillet 2013
Langue : English
Type : Texte
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Valkaama DVD Cover Outside
4 octobre 2011, par
Mis à jour : Octobre 2011
Langue : English
Type : Image
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Valkaama DVD Label
4 octobre 2011, par
Mis à jour : Février 2013
Langue : English
Type : Image
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Valkaama DVD Cover Inside
4 octobre 2011, par
Mis à jour : Octobre 2011
Langue : English
Type : Image
Autres articles (77)
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Mise à jour de la version 0.1 vers 0.2
24 juin 2013, parExplications des différents changements notables lors du passage de la version 0.1 de MediaSPIP à la version 0.3. Quelles sont les nouveautés
Au niveau des dépendances logicielles Utilisation des dernières versions de FFMpeg (>= v1.2.1) ; Installation des dépendances pour Smush ; Installation de MediaInfo et FFprobe pour la récupération des métadonnées ; On n’utilise plus ffmpeg2theora ; On n’installe plus flvtool2 au profit de flvtool++ ; On n’installe plus ffmpeg-php qui n’est plus maintenu au (...) -
Personnaliser en ajoutant son logo, sa bannière ou son image de fond
5 septembre 2013, parCertains thèmes prennent en compte trois éléments de personnalisation : l’ajout d’un logo ; l’ajout d’une bannière l’ajout d’une image de fond ;
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Ecrire une actualité
21 juin 2013, parPrésentez les changements dans votre MédiaSPIP ou les actualités de vos projets sur votre MédiaSPIP grâce à la rubrique actualités.
Dans le thème par défaut spipeo de MédiaSPIP, les actualités sont affichées en bas de la page principale sous les éditoriaux.
Vous pouvez personnaliser le formulaire de création d’une actualité.
Formulaire de création d’une actualité Dans le cas d’un document de type actualité, les champs proposés par défaut sont : Date de publication ( personnaliser la date de publication ) (...)
Sur d’autres sites (12160)
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Dumping and playing h264 bytestream from RTSP webcam
18 octobre 2011, par thekMy goal is to connect (rtsp) to camera, get h264 stream from rtp packages, save it as a bytestream to file and be able to play it (with ffplay or vlc). The only problem is that my result stream gives me errors (and a nice gray rectangle, sometimes with something moving - like only P frames are decoded) while playing.
Here is my DESCRIBE response from rtsp server (ip replaced with ) :
10:04:18.387 [New I/O client worker #1-1] INFO rtsp.WebcamClientResponseHandler - Sending DESCRIBE request: DESCRIBE rtsp://<server>:<port>/channel1 RTSP/1.0
-------status---------
200 OK
-------headers---------
CSeq : 2
Date : Wed, Jan 07 2009 19:05:09 GMT
Content-Base : rtsp://<server>/channel1/
Content-Type : application/sdp
Content-Length : 433
-------content---------
v=0
o=- 515949295799 1 IN IP4 <server>
s=Session streamed by stream
i=1
t=0 0
a=tool:LIVE555 Streaming Media v2009.01.26
a=type:broadcast
a=control:*
a=range:npt=0-
a=x-qt-text-nam:Session streamed by stream
a=x-qt-text-inf:1
m=video 0 RTP/AVP 96
c=IN IP4 0.0.0.0
b=AS:128
a=rtpmap:96 H264/90000
a=fmtp:96 packetization-mode=1;profile-level-id=420028;sprop-parameter-sets=Z0IAKOkCg/I=,aM44gA==
a=control:tracks
</server></server></port></server>And server sends me RTP packages with non IDR frames and fragmented (type=28) IDR frames. First ones are written to file, fragmented are unpacked.
The result byte stream is :NAL SPS NAL PPS NAL FRAME1 NAL FRAME2 ... NAL FRAMEN
where NAL is (hex) 00 00 01
and SPS is (decoded Z0IAKOkCg/I= from sprop-parameter-sets): 67 42 00 28 e9 02 83 f2
and PPS is (decoded aM44gA==): 68 ce 38 80I found similar topic with same steps taken :
how-to-process-raw-udp-packets-so-that-they-can-be-decoded-by-a-decoder-filter-i
but I can't see what am I missing.Could anyone give me some clue what may be wrong ?
This is a link to generated h264 file :
a.h264Below I'm attaching some more information from playing my stream.
Playing my video with ffplay -f h264 a.h264 gives me following output (and a gray rectangle) :
ffplay version 0.8.4-4:0.8.4-0ubuntu1~jon1, Copyright (c) 2003-2011 the FFmpeg developers
built on Sep 25 2011 09:45:09 with gcc 4.4.3
configuration: --extra-version='4:0.8.4-0ubuntu1~jon1' --prefix=/usr --enable-vdpau --enable-bzlib --enable-libgsm --enable-libschroedinger --enable-libspeex --enable-libtheora --enable-libvorbis --enable-pthreads --enable-zlib --enable-libvpx --enable-runtime-cpudetect --enable-vaapi --enable-gpl --enable-postproc --enable-swscale --enable-x11grab --enable-libdc1394 --enable-shared --disable-static
libavutil 51. 9. 1 / 51. 9. 1
libavcodec 53. 7. 0 / 53. 7. 0
libavformat 53. 4. 0 / 53. 4. 0
libavdevice 53. 1. 1 / 53. 1. 1
libavfilter 2. 23. 0 / 2. 23. 0
libswscale 2. 0. 0 / 2. 0. 0
libpostproc 52. 0. 0 / 52. 0. 0
[h264 @ 0x184d4c0] Missing reference picture
[h264 @ 0x184d4c0] decode_slice_header error
[h264 @ 0x184d4c0] concealing 300 DC, 300 AC, 300 MV errors
[h264 @ 0x1822640] max_analyze_duration 5000000 reached at 5000000
[h264 @ 0x1822640] Estimating duration from bitrate, this may be inaccurate
Input #0, h264, from 'a.h264':
Duration: N/A, bitrate: N/A
Stream #0.0: Video: h264 (Baseline), yuv420p, 320x240, 25 fps, 25 tbr, 1200k tbn, 50 tbc
[h264 @ 0x184d4c0] Missing reference pictureq= 3KB sq= 0B f=0/0
[h264 @ 0x184d4c0] decode_slice_header error
[h264 @ 0x184d4c0] concealing 300 DC, 300 AC, 300 MV errors
[h264 @ 0x184d4c0] QP 4294967283 out of rangeKB sq= 0B f=0/0 0/0
[h264 @ 0x184d4c0] decode_slice_header error
[h264 @ 0x184d4c0] concealing 300 DC, 300 AC, 300 MV errors
[h264 @ 0x184d4c0] Missing reference picture
[h264 @ 0x184d4c0] decode_slice_header error
[h264 @ 0x184d4c0] mmco: unref short failure
[h264 @ 0x184d4c0] concealing 300 DC, 300 AC, 300 MV errors
[h264 @ 0x184d4c0] P sub_mb_type 5 out of range at 8 0
[h264 @ 0x184d4c0] error while decoding MB 8 0
[h264 @ 0x184d4c0] concealing 300 DC, 300 AC, 300 MV errors
[h264 @ 0x184d4c0] QP 4294967283 out of range
[h264 @ 0x184d4c0] decode_slice_header error
[h264 @ 0x184d4c0] concealing 300 DC, 300 AC, 300 MV errorsRunning h264_analyse (http://h264bitstream.sourceforge.net/) on my stream gives me :
./h264_analyze a.h264
!! Found NAL at offset 3 (0x0003), size 8 (0x0008)
==================== NAL ====================
forbidden_zero_bit : 0
nal_ref_idc : 3
nal_unit_type : 7 ( Sequence parameter set )
======= SPS =======
profile_idc : 66
constraint_set0_flag : 0
constraint_set1_flag : 0
constraint_set2_flag : 0
constraint_set3_flag : 0
reserved_zero_4bits : 0
level_idc : 40
seq_parameter_set_id : 0
chroma_format_idc : 0
residual_colour_transform_flag : 0
bit_depth_luma_minus8 : 0
bit_depth_chroma_minus8 : 0
qpprime_y_zero_transform_bypass_flag : 0
seq_scaling_matrix_present_flag : 0
log2_max_frame_num_minus4 : 0
pic_order_cnt_type : 0
log2_max_pic_order_cnt_lsb_minus4 : 1
delta_pic_order_always_zero_flag : 0
offset_for_non_ref_pic : 0
offset_for_top_to_bottom_field : 0
num_ref_frames_in_pic_order_cnt_cycle : 0
num_ref_frames : 1
gaps_in_frame_num_value_allowed_flag : 0
pic_width_in_mbs_minus1 : 19
pic_height_in_map_units_minus1 : 14
frame_mbs_only_flag : 1
mb_adaptive_frame_field_flag : 0
direct_8x8_inference_flag : 1
frame_cropping_flag : 0
frame_crop_left_offset : 0
frame_crop_right_offset : 0
frame_crop_top_offset : 0
frame_crop_bottom_offset : 0
vui_parameters_present_flag : 0
=== VUI ===
aspect_ratio_info_present_flag : 0
aspect_ratio_idc : 0
sar_width : 0
sar_height : 0
overscan_info_present_flag : 0
overscan_appropriate_flag : 0
video_signal_type_present_flag : 0
video_format : 0
video_full_range_flag : 0
colour_description_present_flag : 0
colour_primaries : 0
transfer_characteristics : 0
matrix_coefficients : 0
chroma_loc_info_present_flag : 0
chroma_sample_loc_type_top_field : 0
chroma_sample_loc_type_bottom_field : 0
timing_info_present_flag : 0
num_units_in_tick : 0
time_scale : 0
fixed_frame_rate_flag : 0
nal_hrd_parameters_present_flag : 0
vcl_hrd_parameters_present_flag : 0
low_delay_hrd_flag : 0
pic_struct_present_flag : 0
bitstream_restriction_flag : 0
motion_vectors_over_pic_boundaries_flag : 0
max_bytes_per_pic_denom : 0
max_bits_per_mb_denom : 0
log2_max_mv_length_horizontal : 0
log2_max_mv_length_vertical : 0
num_reorder_frames : 0
max_dec_frame_buffering : 0
=== HRD ===
cpb_cnt_minus1 : 0
bit_rate_scale : 0
cpb_size_scale : 0
initial_cpb_removal_delay_length_minus1 : 0
cpb_removal_delay_length_minus1 : 0
dpb_output_delay_length_minus1 : 0
time_offset_length : 0
!! Found NAL at offset 14 (0x000E), size 4 (0x0004)
==================== NAL ====================
forbidden_zero_bit : 0
nal_ref_idc : 3
nal_unit_type : 8 ( Picture parameter set )
======= PPS =======
pic_parameter_set_id : 0
seq_parameter_set_id : 0
entropy_coding_mode_flag : 0
pic_order_present_flag : 0
num_slice_groups_minus1 : 0
slice_group_map_type : 0
num_ref_idx_l0_active_minus1 : 0
num_ref_idx_l1_active_minus1 : 0
weighted_pred_flag : 0
weighted_bipred_idc : 0
pic_init_qp_minus26 : 0
pic_init_qs_minus26 : 0
chroma_qp_index_offset : 0
deblocking_filter_control_present_flag : 0
constrained_intra_pred_flag : 0
redundant_pic_cnt_present_flag : 0
transform_8x8_mode_flag : 1
pic_scaling_matrix_present_flag : 0
second_chroma_qp_index_offset : 16
!! Found NAL at offset 21 (0x0015), size 480 (0x01E0)
==================== NAL ====================
forbidden_zero_bit : 0
nal_ref_idc : 2
nal_unit_type : 1 ( Coded slice of a non-IDR picture )
======= Slice Header =======
first_mb_in_slice : 0
slice_type : 5 ( P slice only )
pic_parameter_set_id : 0
frame_num : 1
field_pic_flag : 0
bottom_field_flag : 0
idr_pic_id : 0
pic_order_cnt_lsb : 2
delta_pic_order_cnt_bottom : 0
redundant_pic_cnt : 0
direct_spatial_mv_pred_flag : 0
num_ref_idx_active_override_flag : 0
num_ref_idx_l0_active_minus1 : 0
num_ref_idx_l1_active_minus1 : 0
cabac_init_idc : 0
slice_qp_delta : -7
sp_for_switch_flag : 0
slice_qs_delta : 0
disable_deblocking_filter_idc : 0
slice_alpha_c0_offset_div2 : 0
slice_beta_offset_div2 : 0
slice_group_change_cycle : 0
=== Prediction Weight Table ===
luma_log2_weight_denom : 0
chroma_log2_weight_denom : 0
luma_weight_l0_flag : 0
chroma_weight_l0_flag : 0
luma_weight_l1_flag : 0
chroma_weight_l1_flag : 0
=== Ref Pic List Reordering ===
ref_pic_list_reordering_flag_l0 : 0
ref_pic_list_reordering_flag_l1 : 0
=== Decoded Ref Pic Marking ===
no_output_of_prior_pics_flag : 0
long_term_reference_flag : 0
adaptive_ref_pic_marking_mode_flag : 0
!! Found NAL at offset 504 (0x01F8), size 324 (0x0144)
==================== NAL ====================
forbidden_zero_bit : 0
nal_ref_idc : 2
nal_unit_type : 1 ( Coded slice of a non-IDR picture )
======= Slice Header =======
first_mb_in_slice : 0
slice_type : 5 ( P slice only )
pic_parameter_set_id : 0
frame_num : 2
field_pic_flag : 0
bottom_field_flag : 0
idr_pic_id : 0
pic_order_cnt_lsb : 4
delta_pic_order_cnt_bottom : 0
redundant_pic_cnt : 0
direct_spatial_mv_pred_flag : 0
num_ref_idx_active_override_flag : 0
num_ref_idx_l0_active_minus1 : 0
num_ref_idx_l1_active_minus1 : 0
cabac_init_idc : 0
slice_qp_delta : -7
sp_for_switch_flag : 0
slice_qs_delta : 0
disable_deblocking_filter_idc : 0
slice_alpha_c0_offset_div2 : 0
slice_beta_offset_div2 : 0
slice_group_change_cycle : 0
=== Prediction Weight Table ===
luma_log2_weight_denom : 0
chroma_log2_weight_denom : 0
luma_weight_l0_flag : 0
chroma_weight_l0_flag : 0
luma_weight_l1_flag : 0
chroma_weight_l1_flag : 0
=== Ref Pic List Reordering ===
ref_pic_list_reordering_flag_l0 : 0
ref_pic_list_reordering_flag_l1 : 0
=== Decoded Ref Pic Marking ===
no_output_of_prior_pics_flag : 0
long_term_reference_flag : 0
adaptive_ref_pic_marking_mode_flag : 0
!! Found NAL at offset 831 (0x033F), size 300 (0x012C)
==================== NAL ====================
forbidden_zero_bit : 0
nal_ref_idc : 2
nal_unit_type : 1 ( Coded slice of a non-IDR picture )
======= Slice Header =======
first_mb_in_slice : 0
slice_type : 5 ( P slice only )
pic_parameter_set_id : 0
frame_num : 3
field_pic_flag : 0
bottom_field_flag : 0
idr_pic_id : 0
pic_order_cnt_lsb : 6
delta_pic_order_cnt_bottom : 0
redundant_pic_cnt : 0
direct_spatial_mv_pred_flag : 0
num_ref_idx_active_override_flag : 0
num_ref_idx_l0_active_minus1 : 0
num_ref_idx_l1_active_minus1 : 0
cabac_init_idc : 0
slice_qp_delta : -7
sp_for_switch_flag : 0
slice_qs_delta : 0
disable_deblocking_filter_idc : 0
slice_alpha_c0_offset_div2 : 0
slice_beta_offset_div2 : 0
slice_group_change_cycle : 0
=== Prediction Weight Table ===
luma_log2_weight_denom : 0
chroma_log2_weight_denom : 0
luma_weight_l0_flag : 0
chroma_weight_l0_flag : 0
luma_weight_l1_flag : 0
chroma_weight_l1_flag : 0
=== Ref Pic List Reordering ===
ref_pic_list_reordering_flag_l0 : 0
ref_pic_list_reordering_flag_l1 : 0
=== Decoded Ref Pic Marking ===
no_output_of_prior_pics_flag : 0
long_term_reference_flag : 0
adaptive_ref_pic_marking_mode_flag : 0
!! Found NAL at offset 1134 (0x046E), size 825 (0x0339)
==================== NAL ====================
forbidden_zero_bit : 0
nal_ref_idc : 2
nal_unit_type : 1 ( Coded slice of a non-IDR picture )
======= Slice Header =======
first_mb_in_slice : 0
slice_type : 5 ( P slice only )
pic_parameter_set_id : 0
frame_num : 4
field_pic_flag : 0
bottom_field_flag : 0
idr_pic_id : 0
pic_order_cnt_lsb : 8
delta_pic_order_cnt_bottom : 0
redundant_pic_cnt : 0
direct_spatial_mv_pred_flag : 0
num_ref_idx_active_override_flag : 0
num_ref_idx_l0_active_minus1 : 0
num_ref_idx_l1_active_minus1 : 0
cabac_init_idc : 0
slice_qp_delta : -9
sp_for_switch_flag : 0
slice_qs_delta : 0
disable_deblocking_filter_idc : 0
slice_alpha_c0_offset_div2 : 0
slice_beta_offset_div2 : 0
slice_group_change_cycle : 0
=== Prediction Weight Table ===
luma_log2_weight_denom : 0
chroma_log2_weight_denom : 0
luma_weight_l0_flag : 0
chroma_weight_l0_flag : 0
luma_weight_l1_flag : 0
chroma_weight_l1_flag : 0
=== Ref Pic List Reordering ===
ref_pic_list_reordering_flag_l0 : 0
ref_pic_list_reordering_flag_l1 : 0
=== Decoded Ref Pic Marking ===
no_output_of_prior_pics_flag : 0
long_term_reference_flag : 0
adaptive_ref_pic_marking_mode_flag : 0
!! Found NAL at offset 1962 (0x07AA), size 754 (0x02F2)
==================== NAL ====================
forbidden_zero_bit : 0
nal_ref_idc : 2
nal_unit_type : 1 ( Coded slice of a non-IDR picture )
======= Slice Header =======
first_mb_in_slice : 0
slice_type : 5 ( P slice only )
pic_parameter_set_id : 0
frame_num : 5
field_pic_flag : 0
bottom_field_flag : 0
idr_pic_id : 0
pic_order_cnt_lsb : 10
delta_pic_order_cnt_bottom : 0
redundant_pic_cnt : 0
direct_spatial_mv_pred_flag : 0
num_ref_idx_active_override_flag : 0
num_ref_idx_l0_active_minus1 : 0
num_ref_idx_l1_active_minus1 : 0
cabac_init_idc : 0
slice_qp_delta : -9
sp_for_switch_flag : 0
slice_qs_delta : 0
disable_deblocking_filter_idc : 0
slice_alpha_c0_offset_div2 : 0
slice_beta_offset_div2 : 0
slice_group_change_cycle : 0
=== Prediction Weight Table ===
luma_log2_weight_denom : 0
chroma_log2_weight_denom : 0
luma_weight_l0_flag : 0
chroma_weight_l0_flag : 0
luma_weight_l1_flag : 0
chroma_weight_l1_flag : 0
=== Ref Pic List Reordering ===
ref_pic_list_reordering_flag_l0 : 0
ref_pic_list_reordering_flag_l1 : 0
=== Decoded Ref Pic Marking ===
no_output_of_prior_pics_flag : 0
long_term_reference_flag : 0
adaptive_ref_pic_marking_mode_flag : 0
!! Found NAL at offset 2719 (0x0A9F), size 824 (0x0338)
==================== NAL ====================
forbidden_zero_bit : 0
nal_ref_idc : 2
nal_unit_type : 1 ( Coded slice of a non-IDR picture )
======= Slice Header =======
first_mb_in_slice : 0
slice_type : 5 ( P slice only )
pic_parameter_set_id : 0
frame_num : 6
field_pic_flag : 0
bottom_field_flag : 0
idr_pic_id : 0
pic_order_cnt_lsb : 12
delta_pic_order_cnt_bottom : 0
redundant_pic_cnt : 0
direct_spatial_mv_pred_flag : 0
num_ref_idx_active_override_flag : 0
num_ref_idx_l0_active_minus1 : 0
num_ref_idx_l1_active_minus1 : 0
cabac_init_idc : 0
slice_qp_delta : -9
sp_for_switch_flag : 0
slice_qs_delta : 0
disable_deblocking_filter_idc : 0
slice_alpha_c0_offset_div2 : 0
slice_beta_offset_div2 : 0
slice_group_change_cycle : 0
=== Prediction Weight Table ===
luma_log2_weight_denom : 0
chroma_log2_weight_denom : 0
luma_weight_l0_flag : 0
chroma_weight_l0_flag : 0
luma_weight_l1_flag : 0
chroma_weight_l1_flag : 0
=== Ref Pic List Reordering ===
ref_pic_list_reordering_flag_l0 : 0
ref_pic_list_reordering_flag_l1 : 0
=== Decoded Ref Pic Marking ===
no_output_of_prior_pics_flag : 0
long_term_reference_flag : 0
adaptive_ref_pic_marking_mode_flag : 0
!! Found NAL at offset 3546 (0x0DDA), size 628 (0x0274)
==================== NAL ====================
[...] -
Ajouter un moyen de voir la configuration de php
27 septembre 2011Il peut être intéressant d’avoir dans la configuration un accès direct aux informations de configuration de PHP pour débugguer un site ...
Pour ce faire, on va rajouté un onglet de configuration dans la partie "Configuration avancée" qui nous permettra en un coup de click d’avoir cette configuration visible.
On ajoute donc une page
ms_configqui montrera le résultat deet le tour sera joué.
-
CD-R Read Speed Experiments
21 mai 2011, par Multimedia Mike — Science Projects, Sega DreamcastI want to know how fast I can really read data from a CD-R. Pursuant to my previous musings on this subject, I was informed that it is inadequate to profile reading just any file from a CD-R since data might be read faster or slower depending on whether the data is closer to the inside or the outside of the disc.
Conclusion / Executive Summary
It is 100% true that reading data from the outside of a CD-R is faster than reading data from the inside. Read on if you care to know the details of how I arrived at this conclusion, and to find out just how much speed advantage there is to reading from the outside rather than the inside.Science Project Outline
- Create some sample CD-Rs with various properties
- Get a variety of optical drives
- Write a custom program that profiles the read speed
Creating The Test Media
It’s my understanding that not all CD-Rs are created equal. Fortunately, I have 3 spindles of media handy : Some plain-looking Memorex discs, some rather flamboyant Maxell discs, and those 80mm TDK discs :
My approach for burning is to create a single file to be burned into a standard ISO-9660 filesystem. The size of the file will be the advertised length of the CD-R minus 1 megabyte for overhead— so, 699 MB for the 120mm discs, 209 MB for the 80mm disc. The file will contain a repeating sequence of 0..0xFF bytes.
Profiling
I don’t want to leave this to the vagaries of any filesystem handling layer so I will conduct this experiment at the sector level. Profiling program outline :- Read the CD-ROM TOC and get the number of sectors that comprise the data track
- Profile reading the first 20 MB of sectors
- Profile reading 20 MB of sectors in the middle of the track
- Profile reading the last 20 MB of sectors
Unfortunately, I couldn’t figure out the raw sector reading on modern Linux incarnations (which is annoying since I remember it being pretty straightforward years ago). So I left it to the filesystem after all. New algorithm :
- Open the single, large file on the CD-R and query the file length
- Profile reading the first 20 MB of data, 512 kbytes at a time
- Profile reading 20 MB of sectors in the middle of the track (starting from filesize / 2 - 10 MB), 512 kbytes at a time
- Profile reading the last 20 MB of sectors (starting from filesize - 20MB), 512 kbytes at a time
Empirical Data
I tested the program in Linux using an LG Slim external multi-drive (seen at the top of the pile in this post) and one of my Sega Dreamcast units. I gathered the median value of 3 runs for each area (inner, middle, and outer). I also conducted a buffer flush in between Linux runs (as root :'sync; echo 3 > /proc/sys/vm/drop_caches').LG Slim external multi-drive (reading from inner, middle, and outer areas in kbytes/sec) :
- TDK-80mm : 721, 897, 1048
- Memorex-120mm : 1601, 2805, 3623
- Maxell-120mm : 1660, 2806, 3624
So the 120mm discs can range from about 10.5X all the way up to a full 24X on this drive. For whatever reason, the 80mm disc fares a bit worse — even at the inner track — with a range of 4.8X - 7X.
Sega Dreamcast (reading from inner, middle, and outer areas in kbytes/sec) :
- TDK-80mm : 502, 632, 749
- Memorex-120mm : 499, 889, 1143
- Maxell-120mm : 500, 890, 1156
It’s interesting that the 80mm disc performed comparably to the 120mm discs in the Dreamcast, in contrast to the LG Slim drive. Also, the results are consistent with my previous profiling experiments, which largely only touched the inner area. The read speeds range from 3.3X - 7.7X. The middle of a 120mm disc reads at about 6X.
Implications
A few thoughts regarding these results :- Since the very definition of 1X is the minimum speed necessary to stream data from an audio CD, then presumably, original 1X CD-ROM drives would have needed to be capable of reading 1X from the inner area. I wonder what the max read speed at the outer edges was ? It’s unlikely I would be able to get a 1X drive working easily in this day and age since the earliest CD-ROM drives required custom controllers.
- I think 24X is the max rated read speed for CD-Rs, at least for this drive. This implies that the marketing literature only cites the best possible numbers. I guess this is no surprise, similar to how monitors and TVs have always been measured by their diagonal dimension.
- Given this data, how do you engineer an ISO-9660 filesystem image so that the timing-sensitive multimedia files live on the outermost track ? In the Dreamcast case, if you can guarantee your FMV files will live somewhere between the middle and the end of the disc, you should be able to count on a bitrate of at least 900 kbytes/sec.
Source Code
Here is the program I wrote for profiling. Note that the filename is hardcoded (#define FILENAME). Compiling for Linux is a simple'gcc -Wall profile-cdr.c -o profile-cdr'. Compiling for Dreamcast is performed in the standard KallistiOS manner (people skilled in the art already know what they need to know) ; the only variation is to compile with the'-D_arch_dreamcast'flag, which the default KOS environment adds anyway.C :-
#ifdef _arch_dreamcast
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#include <kos .h>
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/* map I/O functions to their KOS equivalents */
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#define open fs_open
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#define lseek fs_seek
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#define read fs_read
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#define close fs_close
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#define FILENAME "/cd/bigfile"
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#else
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#include <stdio .h>
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#include <sys /types.h>
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#include </sys><sys /stat.h>
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#include </sys><sys /time.h>
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#include <fcntl .h>
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#include <unistd .h>
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#define FILENAME "/media/Full disc/bigfile"
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#endif
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/* Get a current absolute millisecond count ; it doesn’t have to be in
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* reference to anything special. */
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unsigned int get_current_milliseconds()
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{
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#ifdef _arch_dreamcast
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return timer_ms_gettime64() ;
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#else
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struct timeval tv ;
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gettimeofday(&tv, NULL) ;
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return tv.tv_sec * 1000 + tv.tv_usec / 1000 ;
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#endif
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}
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#define READ_SIZE (20 * 1024 * 1024)
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#define READ_BUFFER_SIZE (512 * 1024)
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int main()
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{
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int i, j ;
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int fd ;
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char read_buffer[READ_BUFFER_SIZE] ;
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off_t filesize ;
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unsigned int start_time, end_time ;
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fd = open(FILENAME, O_RDONLY) ;
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if (fd == -1)
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{
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return 1 ;
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}
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filesize = lseek(fd, 0, SEEK_END) ;
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for (i = 0 ; i <3 ; i++)
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{
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if (i == 0)
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{
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lseek(fd, 0, SEEK_SET) ;
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}
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else if (i == 1)
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{
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lseek(fd, (filesize / 2) - (READ_SIZE / 2), SEEK_SET) ;
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}
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else
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{
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lseek(fd, filesize - READ_SIZE, SEEK_SET) ;
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}
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/* read 20 MB ; 40 chunks of 1/2 MB */
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start_time = get_current_milliseconds() ;
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for (j = 0 ; j <(READ_SIZE / READ_BUFFER_SIZE) ; j++)
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if (read(fd, read_buffer, READ_BUFFER_SIZE) != READ_BUFFER_SIZE)
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{
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break ;
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}
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end_time = get_current_milliseconds() ;
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end_time, start_time, end_time - start_time,
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READ_SIZE / (end_time - start_time)) ;
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}
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close(fd) ;
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return 0 ;
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}
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