Insert size peak

[maisarahabs]

Hi.

I used fastp to trim my ChIP-seq reads. My samples are paired-end reads.

After trimming, the report states that

Insert size peak (evaluated by paired-end reads): 0

Is this normal? What is the meaning of insert size peak here?

[pdimens]

I have also gotten reports like this for my data. Is there any insight into what could be happening here?

Read1 before filtering:
total reads: 1778364
total bases: 238806338
Q20 bases: 227824941(95.4015%)
Q30 bases: 211900527(88.7332%)

Read2 before filtering:
total reads: 1778364
total bases: 225444254
Q20 bases: 203841616(90.4177%)
Q30 bases: 183846152(81.5484%)

Read1 after filtering:
total reads: 1022353
total bases: 126318233
Q20 bases: 121175588(95.9288%)
Q30 bases: 112747279(89.2565%)

Read2 aftering filtering:
total reads: 1022353
total bases: 124441135
Q20 bases: 117016680(94.0338%)
Q30 bases: 106349956(85.4621%)

Filtering result:
reads passed filter: 2044706
reads failed due to low quality: 22264
reads failed due to too many N: 88
reads failed due to too short: 1489670
reads with adapter trimmed: 1985391
bases trimmed due to adapters: 103210714

Duplication rate: 39.327%

Insert size peak (evaluated by paired-end reads): 0

JSON report: ./YFTL_003_S2_L002_R1_001.json
HTML report: ./YFTL_003_S2_L002_R1_001.html

fastp --in1 ./YFTL_003_S2_L002_R1_001.F.fq.gz --in2 ./YFTL_003_S2_L002_R1_001.R.fq.gz --out1 ./YFTL_003_S2_L002_R1_001.R1.fq.gz --out2 ./YFTL_003_S2_L002_R1_001.R2.fq.gz --trim_poly_g --length_required 80 --cut_front --cut_tail --cut_window_size 5 --cut_mean_quality 15 -q 15 -u 50 -j ./YFTL_003_S2_L002_R1_001.json -h ./YFTL_003_S2_L002_R1_001.html --detect_adapter_for_pe --adapter_sequence=AGATCGGAAGAGCACACGTCTGAACTCCAGTCA --adapter_sequence_r2=AGATCGGAAGAGCGTCGTGTAGGGAAAGAGTGT 
fastp v0.20.0, time used: 142 seconds

[sofiapuvogelvittini]

Have you figured out what "Insertion Size Peak (evaluated by paired-end reads): 0" means? Thanks!